Cellulose ester film, polarizing plate and display

ABSTRACT

A cellulose ester film exhibiting: a free volume radius of 0.25 to 0.31 nm and a half-width of 0.04 to 0.1 nm, the free volume radius and the half-width being determined by positron annihilation lifetime spectroscopy; and Ro of 0 to 10 nm and Rt of −30 to ⇄20 nm, Ro and Rt being defined by the following equations: Equation (a): Ro=(nx−ny)×d; Equation (b): Rt=((nx+ny)/2−nz)×d (Ro: in-plane retardation, Rt: retardation in the thickness direction of the film, nx: in-plane refractive index in slow axis direction, ny: in-plane refractive index in fast axis direction, nz: refractive index in the thickness direction of the film (refractive indexes being measured at wavelength of 590 nm), d: thickness of the film (nm)).

This application is based on Japanese Patent Application No. 2005-249038filed on Aug. 30, 2005 in Japanese Patent Office, the entire content ofwhich is hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a cellulose ester film, a polarizingplate, and a display, and in more detail, relates to a cellulose esterfilm which hardly causes a rupture problem during the polarizing plateproduction process employing a cellulose ester film exhibiting reducedoptical anisotropy, and also hardly causes variation of retardationvalues, as well as relates to an in-plane switching mode liquid crystaldisplay having a polarizing plate prepared by using the cellulose esterfilm, the in-plane switching mode liquid crystal display exhibitingexcellent visibility even under changing screen luminance.

BACKGROUND OF THE INVENTION

Along with improvements in performance and quality of liquid crystaldisplays, various demands have been made for polarizing plate protectivefilms employed in polarizing plates.

Commonly employed as the polarizing plate protective film of liquidcrystal displays is film which employs cellulose ester as a material. Inview of assuring flatness, cellulose ester film is commonly producedemploying a solution film-casting method, whereby the refractive indexin the thickness direction of the film tends to be lower than that inthe in-plane direction.

In Patent Document 1, described is a cellulose ester film which resultsin minimal degradation of the polarizer under high temperature and highhumidity, and reduced optical anisotropy due to the incorporation ofethylenic polymers. However, when only ethylenic polymers areincorporated, rupture of the film tends to occur during the produtionprocess of the polarizing plates. Further, it is desirous to reduce thevariation of retardation values. Specifically, it was found that in thehorizontal electric field switching mode type or the in-plane switchingmode (hereinafter referred to as an IPS type) liquid crystal display,when the image area luminance is adjusted based on the ambientbrightness during viewing, visibility such as contrast or color shiftvaried.

Patent Document 1 Japanese Patent Publication for Public Inspection(hereinafter referred to as JP-A) No. 2003-12859

SUMMARY OF THE INVENTION

An object of the present invention is to provide a cellulose ester filmwhich hardly causes a rupture problem during a polarizing plateproduction process employing the cellulose ester film exhibiting reducedoptical anisotropy, and also hardly causes variation of retardationvalues. Further another object of the present invention is to provide anin-plane switching mode liquid crystal display having a polarizing plateprepared by employing the above cellulose ester film, the in-planeswitching mode liquid crystal display exhibiting excellent visibilityeven when the screen luminance varies.

One of the aspects of the present invention to achieve the above objectsis a cellulose ester film exhibiting: a free volume radius of 0.25 to0.31 nm and a half-width of 0.04 to 0.1 nm, the free volume radius andthe half-width being determined by positron annihilation lifetimespectroscopy; and Ro of 0 to 10 nm and Rt of −30 to +20 nm, Ro and Rtbeing defined by the following equations.Ro=(nx−ny)×d   Equation (a)Rt=((nx+ny)/2−nz)×d   Equation (b)

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a typical example of a graph showing a relationship betweenfree volume radius and relative intensity.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The above objects of the present invention are achieved by the followingstructures.

(1) A cellulose ester film exhibiting:

a free volume radius of 0.25 to 0.31 nm and a half-width of 0.04 to 0.1nm, the free volume radius and the half-width being determined bypositron annihilation lifetime spectroscopy; and

Ro of 0 to 10 nm and Rt of −30 to +20 nm, Ro and Rt being defined by thefollowing equations:Ro=(nx−ny)×d   Equation (a)Rt=((nx +ny)/2−nz)×d   Equation (b)wherein Ro represents an in-plane retardation value, Rt represents aretardation value in a thickness direction of the film, nx represents anin-plane refractive index in a slow axis direction, ny represents anin-plane refractive index in a fast axis direction, nz represents arefractive index in the thickness direction of the film (each refractiveindex is determined at a wavelength of 590 nm), and d represents athickness of the film (nm).

(2) The cellulose ester film of Item (1), wherein the film comprises, asan additive, a polymer having a weight average molecular weight of 500to 30000, the polymer being prepared from a monomer having anethylenically unsaturated bond.

(3) The cellulose ester film of Item (1) comprising an additive selectedfrom the group consisting of compounds represented by Formulas (1), (2),(3), (4), (5), (6), (7), (8), (9), (10), (11), (12), (13) and (14):

wherein R¹ and R² each independently represents an alkyl group which mayhave a substituent or an aryl group which may have a substituent,

wherein X² represents B, C—R (wherein R represents a hydrogen atom or asubstituent), or N; and R¹¹, R¹², R¹³, R¹⁴, R¹⁵, R²¹, R²², R²³, R²⁴,R²⁵, R³¹, R³², R³³, R³⁴, and R³⁵ each represent a hydrogen atom or asubstituent,R1—(OH)n   Formula (3)wherein R1 represents an organic group having a valence of n, and nrepresents an integer of 2 or more,

wherein Y³¹ —Y⁷⁰ each independently represent an acyloxy group having1-20 carbon atoms, an alkoxycarbonyl group having 2-20 carbon atoms, anamido group having 1-20 carbon atoms, a carbamoyl group having 1-20carbon atoms or a hydroxyl group; V³¹—V⁴³ each independently represent ahydrogen atom or an aliphatic group having 1-20 carbon atoms; andL³¹-L⁸⁰ each independently represent a single bond or a divalentsaturated linking group having 1-40 total atoms and 0-20 carbon atoms;and V³¹-V⁴³ and L³¹-L⁸⁰ each may further have a substituent,

wherein Q¹, Q², and Q³ each independently represent a group having a 5-or 6-membered hydrocarbon ring or a 5- or 6-membered heterocycle, andthe ring may be combined with another ring to form a condensed ring, and

wherein R¹, R², and R³ each independently represents a hydrogen atom oran alkyl group having 1-5 carbon atoms; X represents a single bond, —O—,—CO—, an alkylene group, or an arylene group; and Y represents ahydrogen atom, an alkyl group, an aryl group or an aralkyl group.

(4) The cellulose ester film of Item (1) exhibiting Rt of−20 nm≦Rt<3 nm.

(5) A polarizing plate having the cellulose ester film of any one ofItems (1) to (4) on one surface of a polarizing film.

(6) The polarizing plate of Item (5) comprising a polarizing filmcontaining polyvinyl alcohol, the polarizing film having a thickness of10 to 20 μm.

(7) The polarizing plate of Item (5) comprising a polarizing filmcontaining ethylene-modified polyvinyl alcohol.

(8) A display comprising the polarizing plate of any one of Items (5) to(7) and a direct backlight.

According to the present invention, it is possible to provide acellulose ester film which hardly results in a rupture of the filmduring a polarizing plate production process employing a cellulose esterfilm of reduced optical anisotropy and also hardly results in variationof the retardation value. Further, it is possible to provide a in-planeswitching mode crystal display fitted with a polarizing plate preparedby employing the above cellulose ester film, which results in excellentvisibility even when the image area luminance varies.

The most preferred embodiment to practice the present invention will nowbe detailed, however the present invention is not limited thereby.

The features of cellulose ester film of the present invention are thatthe free volume radius and a half-value width, determined by a positronannihilation lifetime method, are 0.25-0.31 nm, and 0.04-0.1 nm,respectively, and Ro and Rt defined in the above formula are 0-10 nm and−30-+20, respectively.

It is desirable to adjust the luminance of the image area of displaysbased on the ambient brightness during viewing images. Namely, it ispreferable that in a bright room, images are best viewed by increasingthe luminance of the image area, while in a darker room, images are bestviewed by decreasing the luminance of the image area. Accordingly, it isalso preferable that the brightness of the room is automatically sensedby a sensor, whereby the luminance is automatically varied. However, ithas been discovered that when luminance varies, problems occur in whichvisibility such as an image area contrast or color shift varies. Thereasons for this are not fully understood, but it is assumed that theheat generated by the backlight varies, whereby the visibility varies.

The cellulose ester film of the present invention exhibitscharacteristics such that, as the above range of Ro and Rt shows,optical anisotropy is significantly decreased, and further, the freevolume radius, determined via the positron annihilation lifetimespectroscopy, is 0.25-0.310 nm, while the half-value width is 0.04-0.1nm, none of which values have been achieved by conventional celluloseester films. Consequently, the above drawbacks may be overcome byemploying a polarizing plate in which the cellulose ester film of thepresent invention is employed in the polarizing plate protective film,whereby it was discovered that it was possible to provide a displaywhich results in decreased visibility variation even when luminancevaries. Namely, it has become possible to provide a liquid crystaldisplay, which automatically varies luminance based on the ambientbrightness.

The present invention will now be detailed below.

The cellulose ester film of the present invention is characterized inthat the free volume radius is 0.25-0.31 nm and the half-width is0.04-0.1 nm, the free volume radius and the half-width being determinedby positron annihilation lifetime spectroscopy.

The free volume radius in the present invention represents vacant areawhich is not occupied by the cellulose ester chain. This free volumeradius can be measured using positron annihilation lifetimespectroscopy. More specifically, by measuring the time from injection ofpositrons into a cellulose ester film to the annihilation of thepositrons, size and numerical concentration of free volume or atomicholes are nondestructively estimated from the annihilation lifetime ofpositrons.

<Measurement of Free Volume Radius by Positron Annihilation LifetimeSpectroscopy>

A positron annihilation lifetime and relative intensity were measuredunder the following measurement condition.

(Measurement Condition)

Positron source: 22NaCl (intensity: 1.85 MBq)

Gamma-ray detector: Plastic scintillator+Photomultiplier tube

Apparatus time resolution: 290 ps

Measurement temperature: 23° C.

Total number of counts: 1 million counts

Specimen size: 20 pieces of 20 mm×15 mm sized films were piled toprepare an about 2 mm thick sample. The sample was dried under vacuum 24hours.

Irradiation area: About 10 mm in diameter

Time per channel: 23.3 ps/ch

According to the above measurement condition, positron annihilationlifetime spectroscopy was carried out. Using a nonlinear least-squaremethod, three components of cellulose ester films were analyzed. Whenthe annihilation times were referred to as, in small order, τ1, τ2 andτ3 and the corresponding intensities were referred to as I1, I2 and I3(I1+I2+I3=100%), respectively, using the largest annihilation time τ3, afree volume radius R3 (nm) was determined using the following formula.The larger the τ3 value is, the larger the free volume is estimated tobe.τ3=(½)[1−(R3/(R3+0.166)}+(½π)sin{2πR3/(R3+0.166)}]−1where, 0.166 (nm) represents the thickness of the electronic layer whichis exuding from the wall of a hole.

The above measurement was repeated twice, and using the peak and theshape of the peak determined from the relative intensity and free volumeradius, its average value and a full width at half maximum (half-width)were determined. In FIG. 1, a graph representing a typical relationshipbetween relative intensity and free volume radius is shown. The relativeintensity represents a relative existing probability of free volume. InFIG. 1, the unit of the relative intensity is arbitrary. The abovementioned half-width is, for example, the half-width shown in FIG. 1.

Evaluation of a free volume in polymer by positron annihilation lifetimespectroscopy is explained in, for example, MATERIAL STAGE vol. 4, No. 5,2004, pp. 21-25, The TRC News, No. 80 (July, 2002) PP. 20-22 (publishedby Toray Research Center Inc.), and “BUNSEKI”, 1988, pp. 11-20”.

The free volume radius of the cellulose ester film of the presentinvention is 0.250-0.310 nm and the half-width is 0.04-0.100 nm. Thefree volume radius of the film of the present invention preferablyspread in the range of 0.20 nm-0.40 nm and the peak of the free volumeradius lies in the range of 0.25-0.30 nm. No cellulose ester film havinga peak of free volume radius less than 0.25 nm has been found so far.The cellulose ester film of the present invention having a free volumeradius of 0.250-0.305 nm is preferable because it tends not causerupture of the film. The half-width is preferably 0.040-0.095, morepreferably 0.045-0.090 and still more preferably 0.070-0.090. Nocellulose ester film exhibiting a half-width less than 0.040 nm has beenfound so far.

The method to control the free volume radius within the prescribed rangeis not specifically limited, however, it can be controlled by thefollowing method.

A cellulose ester film having a free volume radius of 0.250-0.310 nmdetermined by positron annihilation lifetime spectroscopy is obtained bythe following method: casting a dope containing at least a plastcizerand cellulose ester to form a web; stretching the web while the webstill contains a solvent; drying the web until an amount of residualsolvent decreases to 0.3% to obtain a cellulose ester film; treating thefilm at 105-170° C. under a rate of atmosphere replacement of 12 times/hor more or more preferably 12-45 times/h while the web is transported.

The rate of atmosphere replacement is the number of times replacing theatmosphere of a heat treatment chamber by fresh-air per unit time,provided that the volume of the heat treatment chamber is expressed as V(m³) and the amount of fresh-air sent to the heat treatment chamber isexpressed as FA (m³/h). Fresh-air does not include the air which isrecycled and circulating, among the air sent to the heat treatmentchamber but includes the air containing no evaporated solvent norevaporated plasticizer, or the air from which evaporated solvent orevaporated plasticizer are removed.Rate of atmosphere replacement=FA/V(times/h)

When the heat treatment temperature exceeds 155° C., or when it is lowerthan 105° C., the effect of the present invention tends not be acquired.

As the treatment temperature, it is still more preferable that thetreatment temperature is in the range of 120-160° C. Further, preferableis that the heat treatment is carried out under the condition in whichthe rate of atmosphere replacement is 12 times/h or more. When it isless than 12 times/h, the effect of the present invention tends not beacquired.

When the rate of atmosphere replacement is 12 times/h or more, theconcentration of the plasticizer evaporated from the cellulose esterfilm in the atmosphere is thoroughly reduced, accordingly, re-depositionof the plasticizer to the retardation film is also reduced. This isassumed to contribute in attaining the effect of the present invention.When the rate of atmosphere replacement is increased more thannecessary, the production cost increases and due to the fluttering ofthe web, retardation patch increases. Accordingly, it is not recommendedthat the rate of atmosphere replacement is increased more thannecessary, however, after the web was thoroughly dried and the amount ofresidual solvent is considerably decreased, it can be increased.However, the rate of atmosphere replacement of 45 times/h or more is notpractical since the production cost drastically increases. The heattreatment under the rate of atmosphere replacement of 12 times/h or moreis preferably carries out within 1 minute-1 hour. If the treatment timeis less than 1 minute, the free volume radius within a prescribed rangemay be difficult to obtain, while, when it is not more than 1 hour, thechange of retardation value is allowable.

Further, in this process, a pressurizing treatment of the retardationfilm in the thickness direction may also be effectively carried out tocontrol the free energy volume radius within more preferable range. Thepressure is preferably 0.5-10 kPa. The amount of residual solvent at thestage when the pressurizing treatment is carried out is preferably lessthan 0.3%. When the amount of residual solvent is larger, namely, 0.3%or more, the effect of the present invention cannot fully be reduced,although flatness of the cellulose ester film may be improved.

A conventional cellulose ester film which was not subjected to the abovementioned treatments showed a free volume radius larger than 0.315.

In order to decrease the optical anisotropy so that Ro and Rt, definedby the above formulas, reach the range of 0-10 nm and −3-+20 nm,respectively, it is preferable that the cellulose ester film of thepresent invention incorporates, as an additive, polymers synthesizedemploying monomers having an ethylenically unsaturated bond, oradditives selected from those represented by above Formulas (1)-(14).

The following Polymers X and Y are most preferably cited as a polymersynthesized employing monomers incorporating an ethylenicallyunsaturated bond.

Polymer X includes polymers at a weight average molecular weight of2,000-30,000, which are prepared by copolymerizing EthylenicallyUnsaturated Monomer Xa incorporating neither an aromatic ring nor ahydrophilic group in the molecule, and Ethylenically Unsaturated MonomerXb incorporating no aromatic ring but incorporating a hydrophilic groupin the molecule. Polymer Y includes polymers at a weight averagemolecular weight of 500-3,000 prepared by polymerizing EthylenicallyUnsaturated Monomer Y incorporating no aromatic ring. It is preferablethat polymers such as Polymer X or Y, synthesized employing monomersincorporating the ethylenically unsaturated bond, are employed togetherwith other additives and the compounds represented by Formulas (1)-(14).

It is preferable that the cellulose ester of the present inventionsimultaneously incorporates above Polymers X and Y. When Polymer X isemployed together with Polymer Y, it is preferable that the weightaverage molecular weight of Polymer Y<the weight average molecularweight of Polymer X, and the weight average molecular weight of PolymerY+500<the weight average molecular weight of Polymer X≦30,000.

<Polymer X and Polymer Y>

It is generally known that, a material having an aromatic ring in amonomer, specifically, in the primary chain exhibits positivebirefringence in the same manner as a cellulose ester, accordingly, itis preferable to incorporate a material exhibiting negativebirefringence into a cellulose ester film so that retardation value Rtof the cellulose ester film is not negated.

In Polymer X of the present invention, Xa is preferably an acryl or amethacryl monomer having neither an aromatic ring nor a hydrophilicgroup, and Xb is preferably an acryl or a methacryl monomer having noaromatic ring but having a hydrophilic group. In the present invention,polymer X is prepared via copolymerization using hydrophobic monomer Xaand hydrophilic monomer Xb. In Polymer X, these monomers are thepredominant monomers, however, other monomers may be incorporated.

Polymer X of the present invention is represented by Formula (15).−(Xa)m−(Xb)n−(Xc)p−  Formula (15)Polymer X is more preferably a polymer represented by the followingFormula (15-1).—[CH₂—C(—R₁)(—CO₂R₂)]m−[CH₂—C(—R₃)(—CO₂R₄—OH)—]n−(Xc)p−  Formula (15-1)wherein R₁ and R₃ each represents H, or CH₃; R₂ represents an alkylgroup having 1-12 carbon atoms, R₄ represents —CH₂—, —C₂H₄— or —C₃H₆—,Xc represents a monomer unit polymerizable with Xa, Xb, and m, n and peach represents the molar ratio, provided that m≠0, n≠0, and m+m+p=100.

In the following, monomers as a monomer unit constituting Polymer X ofthe preset invention will be cited, however the present invention is notlimited thereto.

Examples of Ethylenically Unsaturated Monomer Xa incorporating neitheran aromatic ring nor a hydrophilic group in the molecule include: methylacrylate, ethyl acrylate, propyl (i- or n-) acrylate, butyl (n-, i-, s-,or t-) acrylate, pentyl (n-, i-, or s-) acrylate, hexyl (n- or i-)acrylate, heptyl (n- or i-) acrylate, octyl (n- or i-) acrylate, nonyl(n- or i-) acrylate, myristyl (n- or i-) acrylate, 2-ethylhexylacrylate, ε-caprolactone acrylate, 2-hydroxyethyl acrylate, and2-ethoxyethyl acrylate, and those in which the above acrylate esters areconverted to methacrylate esters. Of these, preferred are methylacrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, andpropyl (i- or n-) methacrylate.

Preferred as Ethylenically Unsaturated Monomer Xb incorporating noaromatic ring but incorporating a hydrophilic group in the molecule areacrylic or methacrylic acid esters as a monomer unit incorporating ahydroxyl group. Examples include 2-hydroxyethyl acrylate,2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, 4-hydroxybutylacrylate, and 2-hydroxybutyl acrylate, as well as those in which theabove acrylate esters are converted to methacrylate esters. Of these,preferable are 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate,2-hydroxypropyl acrylate and 3-hydroxypropyl acrylate.

The ratio of use of Hydrophobic Monomer Xa to Hydrophilic Monomer Xbduring synthesis is preferably in the range of 99:1−65:35, but is morepreferably in the range of 95:5−75:25. When the ratio of HydrophobicMonomer Xa increases, compatibility with cellulose ester is enhancedwhile retardation value Rt in the film thickness direction increases.Further, when the ratio of Hydrophilic Monomer Xb is increased, thecompatibility with cellulose ester is reduced, however, the effect tolower Rt is enhanced. Also, the ratio of Hydrophilic Monomer Xb in theabove range is preferable, since it is thereby possible to prepare acellulose ester film which exhibits excellent transparency. Xc is notspecifically limited, provided that it is a polymerizable ethlenicallyunsaturated monomer other than Xa and Xb, however, it preferably doesnot contain an aromatic ring. The p value of Xc is 0-10. Xc may be aplurality of monomer units.

In order to synthesize such polymers, it is preferable to employ amethod which does not excessively increase the molecular weight, butresults as much as possible in uniform molecular weight since it isdifficult to control the molecular weight employing a commonpolymerization method. Examples of such methods include a method inwhich peroxide polymerization initiators such as cumene peroxide ort-butylhydroperoxide are employed; a method in which polymerizationinitiators in a larger amount than the common polymerization isemployed; a method in which other than polymerization initiators, chaintransfer agents such as a mercapto compound or carbon tetrachloride areemployed; a method in which other than polymerization initiators,polymerization terminating agents such as benzoquinone or dinitrobenzeneare employed; and a method in which block polymerization is performedemploying polymerization catalysts employing compounds incorporating onethiol group and a secondary hydroxyl group, or incorporating the abovecompound and organic metal compounds, described in JP-A Nos. 2000-128911and 2000-344823. Of these, the methods described in the above patentdocuments are particularly preferred.

The hydroxyl group value of Polymer X is preferably 10-200 mg KOH/g, butis most preferably 30-150 mg KOH/g.

(Measurement Method of Hydroxyl Group Value)

Hydroxyl group value, as described herein, is determined based on JIS K0070 (1992), and is defined as mg of potassium hydroxide consumed toneutralize acetic acid bonded to a hydroxyl group when 1 g of the sampleis acetylated. In practice, X g (approximately 1 g) of a sample, whichhas been accurately weighed, is placed in a flask, and precisely 20 mlof an acetylation reagent (prepared in such a manner that pyridine isadded to 20 ml of acetic anhydride to reach a total volume of 400 ml) isadded. An air cooling pipe is fitted to the opening of the flask and theflask is heated at 95-100 ° C. in a glycerin bath. After one hour and ahalf, the temperature is lowered and 1 ml of pure water is fed throughthe air cooling pipe, whereby acetic anhydride is decomposed to aceticacid. Subsequently, by employing a potentiometric titrator, titration iscarried out via a 0.5 mol/L potassium hydroxide ethanol solution, andwhen the titration curve results in inflection, titration is terminated.Further, as a blank test, titration is carried out without adding thesample and the inflection point of the titration curve is recorded. Thehydroxyl group value is calculated based on the following formula:Hydroxyl group value=((B−C)×f×28.05/X}+Dwherein B represents the volume (ml) of the 0.5 mol/L potassiumhydroxide methanol solution employed in the blank test; C represents thevolume (ml) of the 0.5 mol/L potassium hydroxide methanol solutionemployed for titration; f represents the factor of the 0.5 mol/Lpotassium hydroxide methanol solution; and D represents the acid value,while 28.05 is ½ of 56.11 which is the amount of one mol of potassiumhydroxide.

The weight average molecular weight of Polymer X is preferably2,000-30,000, but is more preferably 2,000-25,000.

A large molecular weight is preferred since it results in advantagessuch that the dimensional change of cellulose ester films under hightemperature and high humidity is significantly decreased and theresulting polarizing plate protective film exhibits reduced curling.When the weight average molecular weight exceeds 30,000, bleed-out underhigh temperature and high humidity, as well as haze formationimmediately after casting, occurs due to poor compatibility withcellulose ester.

It is possible to control the weight average molecular weight ofpolymers of the present invention, employing conventional molecularweight controlling methods. Listed as one such method is incorporatingchain transfer agents such as carbon tetrachloride, lauryl mercaptan, oroctyl thioglycolate. The polymerization temperature is commonly roomtemperature to 130° C., but is preferably 50 to 100° C. It is alsopossible to control the weight average molecular weight by controllingthe above temperature or the polymerization reaction time.

It is further possible to determine the weight average molecule weight,employing the following method.

(Method of Measurement of Molecular Weight)

The weight average molecular weight is determined employing gelpermeation chromatography.

Measurement conditions are as follows:

Solvent: methylene chloride

Columns: SHODEX K806, K805, and K803G (produced by Showa Denko K. K.,employed by connecting above three columns)

Column temperature: 25° C.

Sample concentration: 0.1% by weight

Detector: RI Model 504 (produced by GL Science Co.)

Pump: L6000 (produced by Hitachi, Ltd.)

Flow rate: 1.0 ml/min

Calibration curve: a calibration curve based on 13 samples of standardPOLYSTYRENE STK standard POLYSTYRENE (produced by TOHSOH Corp.) at an Mwof 500-1,000,000 is employed. Thirteen samples, at almost equalintervals, are employed.

Polymer Y, employed in the present invention, includes a polymer at aweight average molecular weight of 500 or more but 3,000 or less,prepared by polymerizing Ethylenically Unsaturated Monomer Ya having noaromatic ring. Preparation of a polymer having a weight averagemolecular weight of less than 500 is difficult because the amount ofunreacted monomer increases. A polymer having a weight average molecularweight of at most 3,000 are preferably employed since retardation Rt isreadily decreased. Ya is preferably an acryl or a methacryl monomerhaving no aromatic ring.

Polymer Y of the present invention is represented by the followingFormula (16).−(Ya)k−(Yb)q−  Formula (16)Polymer Y is more preferably represented by Formula (16-1).—[CH₂—C(—R₅)(—CO₂R₆)]k−[Yb]q−  Formula (16-1)wherein R₅ represents H or CH₃; R₆ represents an alkyl group having 1-12carbon atoms or a cycloalkyl group; Yb represents a monomer unitpolymerizable with Ya; k and q each represent a molar ratio, providedthat k≠0 and k+q=100.

Yb is not specifically limited, provided that it is polymerizable withYa. Yb may be a plurality of monomer unit. The value of q is preferably0-30.

Examples of Ethylenically Unsaturated Monomer Ya constituting Polymer Y,prepared by polymerizing ethylenically unsaturated monomers having noaromatic ring, include: methyl acrylate, ethyl acrylate, propyl (i- orn-) acrylate, butyl (n-, i-, s-, or t-) acrylate, pentyl (n-, i-, or s-)acrylate, hexyl (n- or i-) acrylate, heptyl (n- or i-) acrylate, octyl(n- or i-) acrylate, nonyl (n- or i-) acrylate, myristyl (n- or i-)acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, ε-caprolactoneacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate,3-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, or 2-hydroxybutylacrylate, 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate; methacrylateesters which are derived from the above acrylate esters by changingacrylate esters to methacrylate esters; unsaturated acids such asacrylic acid, methacrylic acid, maleic acid anhydride, crotonic acid anditaconic acid.

Yb is not specifically limited, however, preferable are vinyl esterssuch as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl valerate,vinyl pivarate, vinyl caprate, vinyl laurate, vinyl myristate, vinylpalmate, vinyl stearate, vinyl cyclohexane carboxylate, vinyl octylate,vinyl methacrylate, vinyl crotonate, vinyl sorbate, and vinyl cinnamate.Yb may be a plurality of monomer unit.

Acryl based polymers are either homopolymers or copolymers of the abovemonomers. The content of methyl acrylate monomer units is preferably atleast 30% by weight, and the content of methyl acrylate monomer units ispreferably at least 40% by weight. Homopolymers of methyl acrylate ormethyl methacrylate are particularly preferred.

Any of the polymers and acryl based polymers prepared by polymerizingthe above ethylenically unsaturated monomers exhibit desiredcompatibility with cellulose ester, excellent productivity due toneither evaporation nor sublimation, desired retention as a polarizingplate protective film, minimal moisture vapor transmittance, andexcellent dimensional stability.

It is preferable that the content of Polymer X and Polymer Y incellulose ester films is preferably in the range satisfying followingFormulas (i) and (ii):5≦Xg+Yg≦35 (% by weight)   Formula (i)0.05≦Yg/(Xg+Yg)≦0.4   Formula (ii)wherein Xg (% by weight) represents the content of Polymer X, while Yg(% by weight) represents the content of Polymer Y.

The preferred range of formula (i) is 10-25% by weight.

The total content of Polymer X and Polymer Y is preferably at least 5%by weight since it is possible to significantly decrease retardationvalue Rt. Further, when the total content exceeds 35% by weight,adhesion to polarizer PVA is degraded.

An increase of Polymer X markedly minimizes degradation of polarizers.However, since retardation value Rt tends to increase, the range tosatisfy above Formula (ii) is preferred to achieve the desired effectsof this invention.

Both Polymers X and Y are employed as a dope constituting component.They may be directly added and dissolved, or may be previously dissolvedin organic solvents and then added to a dope.

Next, the compounds represented by Formula (1) will be described.

In Formula (1), the summation of the number of carbon atoms in R¹ and R²is preferably ten or more.

Examples of a preferable substituent represented by R¹ or R² include: afluorine atom, an alkyl group, an aryl group, an alkoxy group, a sulfonegroup, and a sulfonamide group. Of these, specifically preferable are analkyl group, an aryl group, an alkoxy group, a sulfone group and asulfonamide group.

The alkyl group may be a normal chain alkyl group, a branched chainalkyl group or a cyclic alkyl group. Preferable are alkyl groups having1-25 carbon atoms, more preferably having 6-25 carbon atoms andspecifically preferably having 6 to 20 carbon atoms, examples of whichinclude: a methyl group, an ethyl group, a propyl group, an isopropylgroup, a butyl group, an isobutyl group, a t-butyl group, an amyl group,an isoamyl group, a t-amyl group, a hexyl group, a cyclohexyl group, aheptyl group, an octyl group, a bicyclooctyl group, a nonyl group, anadamantyl group, a decyl group, a t-octyl group, an undecyl group, adodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group,a hexadecyl group, a heptadecyl group, an octadecyl group, a nonadecylgroup and a didecyl group.

As the aryl group, preferable are those having 6-30 carbon atoms andspecifically preferable are those having 6-24 carbon atoms, examples ofwhich include: a phenyl group, a biphenyl group, a terphenyl group, anaphthyl group, a binaphthyl group, a triphenyl group.

Preferable examples of a compound represented by Formula (1) will beshown below, however, the present invention is not limited thereto.

Next, the compounds represented by Formula (2) will be described indetail.

X represents B, C—R (R representing a hydrogen atom or a substituent),N, P, or P═O. Preferably, X represents B, C—R (wherein as examples of R,preferable are an aryl group, a substituted or unsubstituted aminogroup, an alkoxy group, an aryloxy group, an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, an acyloxy group, an acylaminogroup, an alkoxycarbonylamino group, an aryloxycarbonylamino group, asulfonylamino group, a hydroxy group, a mercapto group, a halogen atom(for example, a fluorine atom, a chlorine atom, a bromine atom and aniodine atom) and a carboxyl group; more preferable are an aryl group, analkoxy group, an aryloxygroup, a hydroxy group and a halogen atom;further more preferable are an alkoxy group and a hydroxy group; andspecifically preferable is a hydroxyl group), N and P═O, and morepreferably X represents C—R or N, and specifically preferably Xrepresents C—R.

R¹¹, R¹², R¹³, R¹⁴, R¹⁵, R²¹, R²², R²³, R²⁴, R²⁵, R³¹, R³², R³³, R³⁴ andR³⁵ each independently represent a hydrogen atom or a substituent. As asubstituent, the substituent T which will be described later isapplicable. Preferable examples of R¹¹, R¹², R¹³, R¹⁴, R¹⁵, R²¹, R²²,R²³, R²⁴, R²⁵, R³¹, R³², R³³, R³⁴ and R³⁵ include: an alkyl group, analkenyl group, an alkynyl group, an aryl group, a substituted orunsubstituted amino group, an alkoxy group, an aryloxy group, an acylgroup, an alkoxycarbonyl group, an aryloxycarbonyl group, an acyloxygroup, an acylamino group, an alkoxycarbonylamino group, anaryloxycarbonylamino group, a sulfonylamino group, a sulfamoyl group, acarbamoyl group, an alkylthio group, an arylthio group, a sulfonylgroup, a sulfinyl group, an ureido group, a phosphoric acid amide group,a hydroxy group, a mercapto group, and a halogen atom (for example, afluorine atom, a chlorine atom, a bromine atom and an iodine atom), acyano group, a sulfo group, a carboxyl group, a nitro group, ahydroxamic acid group, a sulfino group, a hydrazino group, an iminogroup, a heterocycle group and a silyl group, more preferably include:an alkyl group, an aryl group, a substituted or unsubstituted aminogroup, an alkoxy group, and an aryloxy group, and further morepreferably include an alkyl group, an aryl group, and an alkoxy group,wherein the heterocycle group preferably has 1 to 30 carbon atoms andmore preferably 1 to 12 carbon atoms, examples of the hetero atominclude: a nitrogen atom, an oxygen atom, a sulfur atom, and a concreteexamples of the hetero group include: an imidazolyl group, a pyridylgroup, a quinolyl group, a furyl group, a piperidyl group, a morpholinogroup, a benzoxazolyl group, a benzimidazolyl group, a benzthiazolylgroup.

These substituents may further be substituted. When two or moresubstituents are contained, those substituents may be the same ordifferent. Moreover, the substituents may be combined to form a ring.

The above mentioned substituent R will now be explained. Exampes of thesubstituent R include: an alkyl group (preferably having 1 to 20 carbonatoms, more preferably having 1 to 12 carbon atoms and still morepreferably having 1 to 8 carbon atoms, and examples of an alkyl groupinclude: a methyl group, an ethyl group, an iso-propyl group, atert-butyl group, an n-octyl group, an n-decyl group, an n-hexadecylgroup, a cyclopropyl group, a cyclopentyl group and a cyclohexyl group);an alkenyl group (preferably having 2 to 20 carbon atoms, morepreferably having 2 to 12 carbon atoms and specifically preferablyhaving 2 to 8 carbon atoms, and examples of the alkenyl group include: avinyl group, an allyl group, a 2-butenyl group and 3-pentenyl group); analkynyl group (preferably having 2 to 20 carbon atoms, more preferablyhaving 2 to 12 carbon atoms and specifically preferably having 2 to 8carbon atoms, and examples of the alkynyl group include: a propargylgroup and a 3-pentynyl group); an aryl group (preferably having 6 to 30carbon atoms, more preferably having 6 to 20 carbon atoms andspecifically preferably having 6 to 12 carbon atoms, and examples of thearyl group include: a phenyl group, a p-methylphenyl group and anaphthyl group); a substituted or unsubstituted amino group (preferablyhaving 0 to 20 carbon atoms, more preferably having 0 to 10 carbon atomsand specifically preferably having 0 to 6 carbon atoms, and examples ofthe amino group include: an amino group, a methylamino group, adimethylamino group, a diethylamino group and a dibenzylamino group); analkoxy goup (preferably having 1 to 20 carbon atoms, more preferablyhaving 1 to 12 carbon atoms and specifically preferably having 1 to 8carbon atoms, and examples of the alkoxy group include: a methoxy group,an ethoxy group and a butoxy group); an aryloxy group (preferably having1 to 20 carbon atoms, more preferably having 1 to 12 carbon atoms andspecifically preferably having 1 to 8 carbon atoms, and examples of thearyloxy group include: a phenyloxy group and a 2-naphthyloxy group); anacyl group (preferably having 1 to 20 carbon atoms, more preferablyhaving 1 to 16 carbon atoms and specifically preferably having 1 to 12carbon atoms, and examples of the, acyl group include: an acetyl group,a benzoyl group, a formyl group and a pivaloyl group); an alkoxycarbonylgroup (preferably having 2 to 20 carbon atoms, more preferably having 2to 16 carbon atoms and specifically preferably having 2 to 12 carbonatoms, and examples of the alkoxycarbonyl group include: amethoxycarbonyl group and an ethoxycarbonyl group); an aryloxycarbonylgroup (preferably having 7 to 20 carbon atoms, more preferably having 7to 16 carbon atoms and specifically preferably having 7 to 10 carbonatoms, and a phenyloxycarbonyl group is cited as an example of thealkoxycarbonyl group); an acyloxy group (preferably having 2 to 20carbon atoms, more preferably having 2 to 16 carbon atoms andspecifically preferably having 2 to 10 carbon atoms, and examples of theacyloxy group include: an acetoxy group and a benzoyloxy group); anacylamino group (preferably having 2 to 20 carbon atoms, more preferablyhaving 2 to 16 carbon atoms and specifically preferably having 2 to 10carbon atoms, and examples of the acylamino group include: anacetylamino group and a benzoylamino group); an alkoxycarbonylaminogroup (preferably having 2 to 20 carbon atoms, more preferably having 2to 16 carbon atoms and specifically preferably having 2 to 12 carbonatoms, and examples of the alkoxycarbonylamino group include: amethoxycarbonylamino group); an aryloxycarbonylamino group (preferablyhaving 7 to 20 carbon atoms, more preferably having 7 to 16 carbon atomsand specifically preferably having 1 to 12 carbon atoms, and examples ofthe aryloxycarbonylamino group include: a phenyloxycarbonylamino group);a sulfonylamino group (preferably having 1 to 20 carbon atoms, morepreferably having 1 to 16 carbon atoms and specifically preferablyhaving 1 to 2 carbon atoms, and examples of the sulfonylamino groupinclude: a methanesulfonylamino group and a benzensulfonylamino group);a sulfamoyl group (preferably having 0 to 20 carbon atoms, morepreferably having 0 to 16 carbon atoms and specifically preferablyhaving 0 to 12 carbon atoms, and examples of the sulfamoyl groupinclude: a sulfamoyl group, a methylsulfamoyl group, a dimethylsulfamoylgroup and a phenylsulfamoyl group); a carbamoyl group (preferably having1 to 20 carbon atoms, more preferably having 1 to 16 carbon atoms andspecifically preferably having 1 to 12 carbon atoms, and examples of thecarbamoyl group include: a carbamoyl group, a methylcarbamoyl group, adiethylcarbamoyl group and a phenylcarbamoyl group); an alkylthio group(preferably having 1 to 20 carbon atoms, more preferably having 1 to 16carbon atoms and specifically preferably having 1 to 12 carbon atoms,and examples of the alkoxy group include: a methylthio group and anethylthio group); an arylthio group (preferably having 6 to 20 carbonatoms, more preferably having 6 to 16 carbon atoms and specificallypreferably having 6 to 12 carbon atoms, and examples of the arylthiogroup include: a phenylthio group); a sulfonyl group (preferably having1 to 20 carbon atoms, more preferably having 1 to 16 carbon atoms andspecifically preferably having 1 to 12 carbon atoms, and examples of thesulfonyl group include: a mesyl group and a tosyl group); a sulfinylgroup (preferably having 1 to 20 carbon atoms, more preferably having 1to 16 carbon atoms and specifically preferably having 1 to 12 carbonatoms, and examples of the sulfinyl group include: a methanesulfinylgroup and a benzenesulfinyl group); an ureido group (preferably having 1to 20 carbon atoms, more preferably having 1 to 16 carbon atoms andspecifically preferably having 1 to 12 carbon atoms, and examples of theureido group include: an ureido group, a methylureido group and aphenylureido group); a phosphoric acid amide group (preferably having 1to 20 carbon atoms, more preferably having 1 to 16 carbon atoms andspecifically preferably having 1 to 12 carbon atoms, and examples of thephosphoric acid amide group include: a 33 7827E diethyl phosphoric acidamide group and a phenyl phosphoric acid amide group);

a hydroxy group; a sulfhydryl group; a halogen atom (for example, afluorine atom and a chlorine atom, a bromine atom and an iodine atom); acyano group; a sulfo group; a carboxyl group; a nitro group; ahydroxamic acid group; a sulfino group; a hydrazino group; an iminogroup; a heterocycle group (preferably having 1 to 30 carbon atoms andmore preferably having 1 to 12 carbon atoms, and examples of a heteroatom include: a nitrogen atom, an oxygen atom and a sulfur atom, andconcrete examples include: an imidazolyl group, a pyridyl group, aquinolyl group, a furyl group, a piperidyl group, a morpholino group, abenzoxazolyl group, a benzimidazolyl group and a benzthiazolyl group);and a silyl group (preferably having 3 to 40 carbon atoms, morepreferably having 3 to 30 carbon atoms and specifically preferablyhaving 3 to 24 carbon atoms, and examples of the silyl group include: atrimethylsilyl group and a triphenylsilyl group). These substituents mayfurther be substituted, and, when two or more substituents are included,they may be the same or different. Further, the substituents may becombined to form a ring.

The present invention will now explained in detail, below, usingspecific examples of a compound represented by Formula (2), however, thepresent invention is not limited thereto.

A polyalcohol ester is prepared by esterification of an aliphaticpolyalcohol of dihydric or more and a monocarboxylic acid. Preferable isan aliphatic monocarboxylic acid ester.

The polyalcohol employed in the present invention is represented by theabove mentioned Formula (3).

Examples of a preferable polyaocohol include: adonitol, arabitol,ethylene glycol, diethylene glycol, triethylene glycol, tetraethyleneglycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol,tripropylene glycol, 1,2-butanediol, 1,3-butanediol, 1.4-butanediol,dibutylene glycol, 1,2,4-bunanetriol, 1,5-pentanediol, 1,6-hexanediol,hexanetriol, galactitol, mannitol, 3-methylpentane-1,3,5-triol, pinacol,sorbitol, trimethylolpropane, trimethylolethane and xylitol, but theinvention is not limited thereto. Specifically, triethylene glycol,tetraethylene glycol, dipropylene glycol, tripropylene glycol, sorbitol,trimethylol propane, xylitol, pentaerythritol and dipentaerythritol.

The monocarboxylic acid to be used in the polyalcohol ester is notspecifically limited and a known aliphatic monocarboxylic acid,alicyclic monocarboxylic acid and aromatic monocarboxylic acid may beemployed. Specifically, aliphatic monocarboxylic acid and aromaticmonocarboxylic acid are preferable, because the moisture permeabilityand the retaninability are improved. Examples of the preferablemonocarboxylic acid are listed below but the present invention is notlimited thereto.

A straight or branched chain carboxylic acid having 1 to 32 carbon atomsis preferably employed as an aliphatic monocarboxylic acid. The numberof carbon atoms is more preferably from 1-20, and specificallypreferably from 1-10. The use of acetic acid is preferable for raisingthe compatibility with a cellulose ester, and the mixing of acetic acidwith another carboxylic acid is also preferable.

As the preferable aliphatic monocarboxylic acid, saturated fatty acidssuch as acetic acid, propionic acid, butylic acid, valeric acid, caproicacid, enantic acid, caprylic acid, pelargonic acid, capric acid,2-ethyl-hexane acid, undecylic acid, lauric acid, tridecylic acid,myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid,stearic acid, nonadecanic acid, arachic acid, behenic acid, lignocelicacid, cerotic acid, heptacosanic acid, montanic acid, melisic acid andlacceric acid; and unsaturated fatty acids such as undecylenic acid,oleic acid, sorbic acid, linolic acid, linolenic acid and arachidonicacid can be exemplified. Examples of preferable alicyclic monocarboxylicacid include cyclopentene carboxylic acid, cyclohexane carboxylic acid,cyclooctane carboxylic acid and derivatives thereof. Examples ofpreferable aromatic monocarboxylic acid include: ones formed byintroducing an alkyl group into the benzene ring of benzoic acid such asbenzoic acid and toluic acid, an aromatic monocarboxylic acid having twoor more benzene rings such as biphenylcarboxylic acid, naphthalenecarboxylic acid and tetralin carboxylic acid and derivatives of them,and benzoic acid is specifically preferable.

The molecular weight of the polyalcohol is preferably from 300 to 1,500,and more preferably from 350 to 1000. Larger molecular weight ispreferable because it is less volatile, while smaller molecular weightis preferable with respect to the moisture permeability andcompatibility with cellulose ester. The carboxylic acid to be employedin the polyalcohol ester may be one kind or a mixture of two or morekinds of them. All the OH groups of the polyalcohol may be esterified ora part of the OH groups may be left unesterified. Specific examples of apolyalcohol will be shown below:

In addition, a trimethylolpropanetriacetate and apentaerythritoltetraacetate are used preferably. The compoundrepresented by one of Formulas (1)-(3) is preferably used in an amountof 0.01-30 weight parts or more preferably 0.5-25 weight parts in 100weight parts of cellulose ester. The compound may be added in a dopeafter dissolved in an organic solvent such as an alcohol, methylenechloride or dioxolane, may be directly added in a dope.

The compounds represented by Formulas (4)-(12) will now be explained.

In Formulas (4)-(12), Y³¹—Y⁷⁰ each independently represent an acyloxygroup having 1-20 carbon atoms, an alkoxycarbonyl group having 2-20carbon atoms, an amide group having 1-20 carbon atoms, a carbamoyl grouphaving 1-20 carbon atoms or a hydroxy group. V³¹—V⁴³, each independentlyrepresent a hydrogen atom or an aliphatic group having 1-20 carbonatoms. L³¹-L⁸⁰ each independently represent a single bond or a saturatedlinking group having total atom number of 0-40 and having 0-20 carbonatoms. V³¹—V⁴³, and L³¹-L⁸⁰ may further have a substituent.

An acyloxy group preferably has 1-16 carbon atoms and more preferably2-12 carbon atoms. Examples of an acyloxy group include: acetoxy,propionyloxy, butyryloxy, vleryloxy, isovaleryloxy,2,2-dimethylpropionyloxy, 2-methylbutyryloxy, hexanoiloxy,2,2-dimethylbutyryloxy, heptanoiloxy, cyclohexyl carbonyloxy,2-ethylhexanoiloxy, octanoyloxy, decanoyloxy, dodecanoiloxy,phenylacetoxy and 1-naphthoyloxy, 2-naphthoyloxy and1-adamantanecarbonyloxy.

An alkoxycarbonyl group preferably has 2-16 carbon atoms and morepreferably has 2-12 carbon atoms. Examples of an alkoxycarbonyl groupinclude: methoxycarbonyl, ethoxycarbonyl, propyloxycarbonyl,isopropyloxycarbonyl, butoxycarbonyl, t-butoxycarbonyl,isobutyloxycarbonyl, sec-butyloxycarbonyl, pentyloxycarbonyl, t-amyloxycarbonyl, hexyloxycarbonyl, cyclohexyloxycarbonyl,2-ethylhexyloxycarbonyl, 1-ethylpropyloxycarbonyl, octyloxycarbonyl,3,7-dimethyl-3-octyloxycarbonyl, 3,5,5-trimethylhexyloxycarbonyl,4-t-butylcyclohexyloxycarbonyl, 2,4-dimethylpentyl-3-oxycarbonyl,1-adamantaneoxycarbonyl, 2-adamantaneoxycarbonyl,dicyclopentadienyloxycarbonyl, decyloxycarbonyl, dodecyloxycarbonyl,tetradecyloxycarbonyl and hexadecyloxycarbonyl.

An amide group preferably has 1-16 carbon atoms and more preferably has1-12 carbon atoms. Examples of an amide group include: acetoamido,propioneamido, butylamido, isobutylamido, pentanamido,2,2-dimethylpropioneamido, 3-methylbutylamido, 3-methylbutylamido,capronamido, 2,2-dimethylbutylamido, heptaneamido,cyclohexylcarboxamido, 2-ethylcapronamido, 2-ethylbutaneamido,caprylamido, nonaneamido, 1-adamantanecarboxamido,2-adamantanecarboxamido, decaneamido, tridecaneamido, hexadecaneamido,and heptadecaneamido.

A carbamoyl group preferably has 2-16 carbon atoms and more preferablyhas 2-12 carbon atoms. Examples of a carbamoyl group includemethylcarbamoyl, dimethylcarbamoyl, ethylcarbamoyl, diethylcarbamoyl,propylcarbamoyl, isopropylcarbamoyl, butylcarbamoyl, t-butylcarbamoyl,isobutylcarbamoyl, sec-butylcarbamoyl, pentylcarbamoyl, t-amylcarbamoyl,hexylcarbamoyl, cyclohexylcarbamoyl, 2-ethylhexylcarbamoyl,2-ethylbutylcarbamoyl, t-octylcarbamoyl, heptylcarbamoyl,octylcarbamoyl, 1-adamantylcarbamoyl, 2-adamantylcarbamoyl,decylcarbamoyl, dodecylcarbamoyl, tetradecylcarbamoyl andhexadecylcarbamoyl.

Examples of the substituent of Y³¹—Y⁷⁰ include: a halogen atom (afluorine atom, a chlorine atom, a bromine atom and an iodine atom), anormal chain, branched chain or cyclo alkyl group (including a bicycloalkyl group or an activated methine group), an alkenyl group, an alkynylgroup, an aryl group, a heterocycle group, an acyl group, analkoxycarbonyl group, an aryloxycarbonyl group, aheterocycle-oxycarbonyl group, a carbamoyl group, an N-acylcarbamoylgroup, an N-sulfonylcarbamoyl group, an N-carbamoylcarbamoyl group, anN-sulfamoylcarbamoyl group, a carbazoyl group, a carboxy group or itssalt, an oxalyl group, an oxamoil group, a cyano group a carbonimideylgroup (a carbonimidoyl group), a formyl group, a hydroxyl group, analkoxy group (including a group in which an ethyleneoxy group or apropyleneoxy group unit is repeated), an aryloxy group, a heterocycleoxygroup, an acyloxy group, an alkoxycarbonyloxy group, anaryloxycarbonyloxy group, a carbamoyloxy group, a sulfonyloxy group, anamino group, an alkylamino group, an arylamino group, aheterocycle-amino group, an amido group, a sulfonamido group, an ureidogroup, a thioureido group, an imide group, an alkoxycarbonylamino group,an aryloxycarbonylamino group, a sulfamoylamino group, a semicarbazidegroup, an ammonio group, the oxamoylamino group, anN-alkylsulfonylureido group, an N-arylsulfonylureido group, anN-acylureido group, an N-acylsulfamoylamino group, a heterocycle groupcontaining a quarternarized nitrogen atom (for example, a pyriziniogroup, imidazolio group, quinolinio group and iso-quinolinio group), anisocyano group, an imino group, an alkylsulfonyl group, an arylsulfonylgroup, an alkylsulfinyl group, an arylsulfinyl group, a sulfo group andits salt, a sulfamoyl group, an N-acylsulfamoyl group, anN-sulfonylsulfamoyl group and its salt, a phosphino group, a phosphinylgroup, a phosphinyloxy group, a phosphinylamino group, a silyl group anda phosphate group.

Y³¹—Y⁷⁰ may form a substituent formed by combining the above-mentionedsubstituent. Examples of a combined substituent include: anethoxyethoxyethyl group, a hydroxyethoxyethyl group and anethoxycarbonylethyl group.

The aliphatic group represented by V³¹—V⁴³ preferably has 1-16 carbonatoms and more preferably has 1-12 carbon atoms. Still more preferableis a linear, branched or cyclo-alkyl group, alkenyl group or alkynylgroup.

Example of an alkyl group include: methyl, ethyl, propyl, isopropyl,butyl, isobutyl, sec-butyl t-butyl, pentyl, t-amyl, hexyl, octyl, decyl,dodecyl, eicosyl, 2-ethylhexyl, cyclopentyl, cyclohexyl, cycloheptyl,2,6-dimethyl cyclohexyl, 4-t-butylcyclohexyl, cyclopentyl, 1-adamantyl,2-adamantyl, and bicyclo[2.2.2]octane-3-yl.

Examples of an alkenyl group include: vinyl, allyl, prenyl, geranyl,oleyl, 2-cyclopentene-1-yl and 2-cyclohexene-1-yl.

Examples of an alkynyl group include: ethynyl and propargyl.

The examples of the substituent represented by of V³¹—V⁴³ are common tothe examples of the substituent represented by Y³¹—Y⁷⁰.

Examples of the linking group represented by L³¹-L⁸⁰ include: analkylene group (for example, methylene, ethylene, propylene,trimethylene, tetramethylene, pentamethylene, hexamethylene,methylethylene and ethylethylene), a divalent cyclic group (for example,cis-1,4-cyclohexylene, trans-1,4-cyclohexylene and1,3-cyclopentylidene), an ether group, a thioether group, an estergroup, an amide group, a sulfone group, a sulfoxide group, a sulfidegroup, a sulfonamide group, an ureylene group and a thioureylene group.

Two or more linking groups may be combined to form a divalent complexlinking group may be formed. Examples of such a complex linking groupinclude: —(CH₂)₂—O—(CH₂)₂—, —(CH₂)₂—O—(CH₂)₂—O—(CH₂)—, —(CH₂)₂—S—(CH₂)₂—and —(CH₂)₂—O(CH₂)₂—O—CO—(CH₂)₂—.

L³¹ to L⁸⁰ may further have a substituent, and examples of such asubstituent include those cited as the substituents which may subctituteR¹¹—R¹³.

Examples of a compound represented by Formula (4)-(12) include: acitrate ester (for example, O-acetyl triethyl citrate, and O-acetyltributyl citrate, acetyl triethyl citrate, acetyl tributyl citrate,O-acetyl tri(ethyloxycarbonylmethylene)citrate); an oleate ester(forexample, ethyl oleate, butyl oleate, 2-ethylhexyl oleate, phenyl oleate,cyclohexyl oleate, octyl oleate); a ricinoleate ester (for example,methylacetyl ricinoleate); a sebacate ester (for example, dibutylsebacate); a carboxylate ester of grycerin (for example, triacetin andtributyrin); a glycolate (for example, butylphthalylbutyl glycolate,ethylphthalylethyl glycolate, methylphthalylethyl glycolate,butylphthalylbutyl glycolate, methylphthalylmethyl glycolate,propylphthalylpropyl glycolate, butylphthalylbutyl glycolate andoctylphthalyloctyl glycolate); a pentaerythritol carboxylate ester (forexample, pentaerythritol tetraacetate and pentaerythritoltetrabutyrate); a dipentaerythritol carboxylate ester (for example,dipentaerythritol hexaacetate, dipentaerythritol hexabutyrate anddipentaerythritol tetraacetate); a carboxylate ester oftrimethylolpropane (for example, trimethylolpropane triacetate,trimethylolpropane diacetate monopropionate, trimethylolpropanetripropionate, trimethylolpropane tributyrate, trimethylolpropanetripyvaloate, a trimethylolpropane tri(t-butyl acetate),trimethylolpropane di-2-ethylhexanate, trimethylolpropanetetra-2-ethylhexanate, trimethylolpropane diacetate monooctanate andtrimethylolpropane tri(cyclohexanecarboxylate)); a pyprolidonecarboxylate ester (for example, 2-pyrrolidone-5-carboxylic acid methylester, 2-pyrrolidone-5-carboxylic acid ethyl ester,2-pyrrolidone-5-carboxylic acid butyl ester and2-pyrrolidone-5-carboxylic acid 2-ethylhexyl ester); a cyclohexanedicarboxylic acid ester (an example, cis-1,2-cyclohexane dicarboxylicacid dibutyl ester, trans-1,2-cyclohexane dicarboxylic acid dibutylester, cis-1,4-cyclohexane dicarboxylic acid dibutyl ester andtrans-1,4-cyclohexane dicarboxylic acid dibutyl ester); and a xylitolcarboxylate ester (for example, xylitol pentaacetate, xylitoltetraacetate and xylitol pentapropionate) are included.

Glycerol ester has been disclosed in JP-A No. 11-246704 officialgazette. Diglycerol ester has been disclosed in JP-A No. 2000-63560.Citrate has been disclosed in JP-A No. 11-92574.

In Formula (13), Q¹, Q² and Q³ each independently represent a grouphaving a 5-membered ring or a 6-membered ring. The ring include ahydrocarbon ring or a hetero ring, and may form a condensed ringtogether with another ring.

The hydrocarbon ring includes, preferably, a substituted orunsubstituted cyclohexane ring, a substituted or unsubstitutedcyclopentane ring and an aromatic hydrocarbon ring, but more preferablyan aromatic hydrocarbon ring.

A single ring or dicyclic aromatic hydrocarbon having 6-30 carbon atomsis preferable (for example, benzene ring or naphthalene ring). Thenumber of carbon atoms is more preferably 6-20. Of these, benzene ringis the most preferable.

The heterocycle preferably contains an oxygen atom, a nitrogen atom, ora sulfur atom as a hetero atom. The heterocycle preferably hasaromaticity.

Examples of a heterocycle include: furan, pyrrole, thiophene, imidazole,pyrazole, pyridine, pyrazine, pyridazine, triazole, triazine, indole,indazole, purine, thiazoline, thiazole, a thiadiazole, oxazoline,oxazole, oxydiazole, quinoline, isoquinoline, phthalazine,naphthylisine, quinoxaline, quinazoline, cinnoline, pteridine, acridine,phenanthroline, phenazine, tetrazole, benzimidazole benzoxazole,benzthiazole, benzotriazole, and tetrazaindene.

Of these, preferable are pyridine, triazine, and quinoline.

Q¹, Q² and Q³ may have a substituent.

Example of a substituent include: an alkyl group, an alkenyl group, analkynyl group, an aryl group, an amino group, a substituted amino group,an alkoxy group, an aryloxy group, an acyl group, an alkoxycarbonylgroup, an aryloxycarbonyl group, an acyloxy group, an amido group, analkoxycarbonylamino group, an aryloxycarbonylamino group, a sulfonamidogroup, a sulfamoyl group, a substituted sulfamoyl group, a carbamoylgroup, a substitution carbamoyl group, an alkylthio group, an arylthiogroup, a sulfonyl group, a sulfinyl group, an ureido group, a phosphoricacid amido group, a hydroxyl group, a mercapto group, a halogen atom (afluorine atom, a chlorine atom, a bromine atom and an iodine atom), acyano group, a sulfo group, a carboxyl group, a nitro group, ahydroxamic acid group, a sulfino group, a hydrazino group, an iminogroup, a heterocycle group and a silyl group. These substituents mayfurther have a substituent and a plurality of substituents may be thesame or different. Further, the substituents may be combined to form aring.

As for the number of carbon atoms of an alkyl group, preferable is 1-20,more preferably 1-12 and still more preferably 1-8. Examples of an alkylgroup include: methyl, ethyl, isopropyl, tert-butyl octyl, decyl,hexadecyl, cyclo propyl, cyclopentyl and cyclohexyl.

The alkenyl group preferably has 2-20 carbon atoms, more preferably 2-12carbon atoms and most preferably 2-8 carbon atoms. Examples of analkenyl group include: vinyl, allyl, 2-butenyl and 3-pentenyl.

The alkynyl group preferably has 2-20 carbon atoms, more preferably 2-12carbon atoms and most preferably 2-8 carbon atoms. Examples of analkynyl group include: propargyl and 3-pentynyl.

The aryl group preferably has 6-30 carbon atoms, more preferably 6-20carbon atoms and most preferably 6-12 carbon atoms. Examples of an arylgroup include: phenyl, p-methylphenyl and naphthyl.

The amino group preferably has 1-20 carbon atoms, more preferably 1-10carbon atoms and most preferably 1-6 carbon atoms. Examples of an aminogroup include: methylamino, dimethylamino, diethylamino anddibenzylamino.

The alkoxy group preferably has 1-20 carbon atoms, more preferably 1-12carbon atoms and most preferably 1-8 carbon atoms. Examples of an alkoxygroup include: methoxy, ethoxy and butoxy.

The aryloxy group preferably has 6-20 carbon atoms, more preferably 6-16carbon atoms and most preferably 6-12 carbon atoms. Examples of anaryloxy group include: phenyloxy and 2-naphthyloxy.

The acyl group preferably has 1-20 carbon atoms, more preferably 1-16carbon atoms and most preferably 1-12 carbon atoms. Examples of an acylgroup include: acetyl, benzoyl, formyl and pivaloyl.

The alkoxycarbonyl group preferably has 2-20 carbon atoms, morepreferably 2-16 carbon atoms and most preferably 2-12 carbon atoms.Examples of an alkoxycarbonyl group include: methoxycarbonyl andethoxycarbonyl.

The aryloxycarbonyl group preferably has 7-20 carbon atoms, morepreferably 7-16 carbon atoms and most preferably 7-10 carbon atoms.Examples of an aryloxycarbonyl group include: phenyloxycarbonyl.

The acyloxy group preferably has 2-20 carbon atoms, more preferably 2-16carbon atoms and most preferably 2-10 carbon atoms. Examples of anacyloxy group include: acetoxy and benzoyloxy.

The amido group preferably has 2-20 carbon atoms, more preferably 2-16carbon atoms and most preferably 2-10 carbon atoms. Examples of an amidogroup include: acetoamido and benzamido.

The alkoxycarbonylamino group preferably has 2-20 carbon atoms, morepreferably 2-16 carbon atoms and most preferably 2-12 carbon atoms.Examples of an alkoxycarbonylamino group include: methoxycarbonylamino.

The aryloxycarbonylamino group preferably has 7-20 carbon atoms, morepreferably 7-16 carbon atoms and most preferably 7-12 carbon atoms.Examples of an aryloxycarbonylamino group include:phenyloxycarbonylamino.

The sulfonamido group preferably has 1-20 carbon atoms, more preferably1-16 carbon atoms and most preferably 1-12 carbon atoms. Examples of asulfonamido group include: methanesulfonamide and benzenesulfonamide.The substituted sulfamoyl group preferably has 1-20 carbon atoms, morepreferably 1-16 carbon atoms and most preferably 1-12 carbon atoms.Examples of a substituted sulfamoyl group include: methylsulfamoyl,dimethylsulfamoyl and phenylsulfamoyl.

The substituted carbamoyl group preferably has 2-20 carbon atoms, morepreferably 2-16 carbon atoms and most preferably 2-12 carbon atoms.Examples of a substituted carbamoy group include: carbamoyl,methylcarbamoyl, diethylcarbamoyl and phenylcarbamoyl.

The alkylthio group preferably has 1-20 carbon atoms, more preferably1-16 carbon atoms and most preferably 1-12 carbon atoms. Examples of analkylthio group include: methylthio and ethylthio.

The arylthio group preferably has 6-20 carbon atoms, more preferably6-16 carbon atoms and most preferably 6-12 carbon atoms. Examples of anarylthio group include: phenylthio.

The sulfonyl group preferably has 1-20 carbon atoms, more preferably1-16 carbon atoms and most preferably 1-12 carbon atoms. Examples of asulfonyl group include: mesyl and tosyl.

The sulfinyl group preferably has 1-20 carbon atoms, more preferably1-16 carbon atoms and most preferably 1-12 carbon atoms. Examples of asulfinyl group include: methanesulfinyl and benzenesulfinyl.

The ureido group preferably has 1-20 carbon atoms, more preferably 1-16carbon atoms and most preferably 1-12 carbon atoms. Examples of anureido group include: ureido, methylureido and phenylureido.

The phosphoric acid amido group preferably has 1-20 carbon atoms, morepreferably 1-16 carbon atoms and most preferably 1-12 carbon atoms.Examples of a phosphoric acid amido group include: diethyl phosphoricacid amido and phenyl phosphoric acid amido.

The heterocycle group preferably has 1-30 carbon atoms and morepreferably 1-12 carbon atoms. Examples of a hetero atom include: anitrogen atom, an oxygen atom and a sulfur atom. Examples of aheterocycle group include: imidazolyl, pyridyl, quinolyl, furyl,piperidyl, morpholino, benzoxazolyl, benzimidazolyl and benzthiazolyl.

The silyl group preferably has 3-40 carbon atoms, more preferably 3-30carbon atoms and most preferably 3-24 carbon atoms. Examples of a silylgroup include: trimethylsilyl and triphenylsilyl.

The compounds represented by Formula (13) will now be described.

In Formula (13), X represents a tervalent group selected from B, C—R (Rrepresents a hydrogen atom or a substituent), N, P, and P═O. As for X,B, C—R, and N are preferable, more preferable are C—R and N, and mostpreferable is C—R.

Example of the substituent, R include: an aryl group, an amino group, asubstituted amino group, an alkoxy group, an aryloxygroup, an acylgroup, an alkoxycarbonyl group, an aryloxycarbonyl group, an acyloxygroup, an acylamino group, an alkoxycarbonylamino group, anaryloxycarbonylamino group, a sulfonylamino group, a hydroxyl group, amercapto group, a halogen atom (for example, a fluorine atom, a chlorineatom, a bromine atom and an iodine atom) and a carboxyl group. Of these,preferable are an aryl group, an alkoxy group, an aryloxy group, ahydroxyl group and a halogen atom, more preferable are an alkoxy groupand a hydroxyl group, and most preferable is a hydroxyl group.

The compound represented by Formula (13) is preferably a compoundrepresented by Formula (a).

In Formula (a), X² represents a tervalent group selected from B, C—R (Rrepresents a hydrogen atom or a substituent), N. The detail of X² iscommon to that of X in Formula (13).

In Formula (a), R¹¹, R¹², R¹³, R¹⁴ R¹⁵, R²¹, R²², R²³, R²⁴, R²⁵, R³¹,R³², R³³, R³⁴, and R³⁵ each represent a hydrogen atom or a substituent.

The detail of the substituent is common to that of the substituent, Q¹,Q² and Q³ in Formula (13).

Preferable examples of R¹¹, R¹², R¹³, R¹⁴, R¹⁵, R²¹, R²², R²³, R²⁴, R²⁵,R³¹, R³², R³³, R³⁴, and R³⁵ include: an alkyl group, an alkenyl group,an alkynyl group, an aryl group, an amino group, a substituted aminogroup, an alkoxy group, an aryloxy group, an acyl group, analkoxycarbonyl group, an aryloxycarbonyl group, an acyloxy group, anamido group, an alkoxycarbonylamino group, an aryloxycarbonylaminogroup, a sulfonamide group, a sulfamoyl group, a substituted sulfamoylgroup, a carbamoyl group, a substituted carbamoyl group, an alkylthiogroup, an arylthio group, a sulfonyl group, a sulfinyl group, an ureidogroup, a phosphoric acid amido group, a hydroxyl group, a mercapto groupand a halogen atom (a fluorine atom, a chlorine atom a bromine atom andan iodine atom), a cyano groups a sulfo group, a carboxyl group, a nitrogroup, a hydroxamic acid group, a sulfino group, a hydrazino group, animino group, a heterocycle group and a silyl group. More preferable arean alkyl group, an aryl group, an amino group, a substituted aminogroup, an alkoxy group and an aryloxygroup, and most preferable are analkyl group, an aryl group and an alkoxy group.

These substituents may further have a substituent, and a plurality ofsubstituents may be the same or different. Further, the substituents maybe combined to form a ring. In Formula (14), preferably, R¹, R², and R³each independently represent a hydrogen atom or an alkyl group having1-5 carbon atoms. Specifically preferably, at least one of R¹, R², andR³ is an alkyl group having 1-3 carbon atoms (for example, methyl,ethyl, propyl, isopropyl, butyl amyl and isoamyl). X preferablyrepresents at least one divalent linking group selected from a singlebond, —O—, —CO—, an alkylene group (preferably having 1 to 6 carbonatoms, and more preferably having 1-3 carbon atoms, for example,methylene, ethylene and propylene), an arylene group (preferably having6 to 24 carbon atoms, and more preferably having 6-12 carbon atoms, forexample, phenylene, biphenylene and naphtylene). More preferably, Xrepresents at least one divalent linking group selected from —O—, analkylene group and an arylene group. Y is preferably a hydrogen atom; analkyl group (preferably having 2 to 25 carbon atoms, and more preferablyhaving 2-20 carbon atoms, for example, ethyl, isopropyl, t-butyl, hexyl,2-ethylhexyl, t-octyl, dodecyl, cyclohexyl, dicyclohexyl and adamantyl);an aryl group (preferably having 6 to 24 carbon atoms, and morepreferably having 6-18 carbon atoms, for example, phenyl, biphenyl,terphenyl and naphthyl); or an aralkyl group (preferably having 7 to 30carbon atoms, and more preferably having 7-20 carbon atoms, for example,benzyl, cresyl, t-butylphenyl, diphenylmethyl and triphenylmethyl).Specifically preferably, Y is an alkyl group, an aryl group or anaralkyl group. As a combination of —X—Y, —X—Y preferably has a totalcarbon number of 0-40, more preferably 1-30, and most preferably 1-25.

Preferable examples of a compound represented by Formula (14) will beshown below however, the present invention is not limited thereto.

In addition, it is preferable to add the following compound to thecellulose ester of the present invention.

(in the formula, Q¹ and Q² each independently represent an aromaticring, X¹ and X² represent a hydrogen atom or a substituent, providedthat at least one of X¹ and X² represents a cyano group, a carbonylgroup, a sulfonyl group or an aromatic heterocycle.) The aromatic ringrepresented by X¹ or X² may be an aromatic hydrocarbon ring or anaromatic heterocycle. These rings may be a single ring or may becombined with another ring to form a condensed ring.

The aromatic hydrocarbon ring is preferably monocyclic or bicyclic andpreferably having 6-30 carbon atoms (for example, a benzene ring, anaphthalene ring). More preferably, the aromatic hydrocarbon ring has 6to 20 carbon atoms, and still more preferably 6-12 carbon atoms.Specifically preferably the aromatic hydrocarbon is benzene.

The aromatic heterocycle preferably contains a nitrogen atom or a sulfuratom. Examples of the heterocycle include: thiophene, imidazole,pyrazole, pyridine, pyrazine, pyridazine, triazole, triazine, indole,indazole, purine, thiazoline, thiazole, a thiadiazole, oxazoline,oxazole, oxydiazole, quinoline, isoquinoline, phthalazine,naphthylizine, quinoxaline, a quinazoline, cinnoline, pteridine,acridine, phenanthroline, phenazine, tetrazole, benzimidazole,benzoxazole, benzthiazole, benzotriazole, tetrazaindene. Preferablearomatic heterocycle includes pyridine, triazine and quinoline.

The aromatic ring represented by Q¹ or Q² is preferably an aromatichydrocarbon ring and more preferably a benzene ring.

Q¹ and Q² may further have a substituent, and the substituent ispreferably substituent T which will be described below. Examples ofsubstituent T include: an alkyl group (preferably having 1 to 20 carbonatoms, more preferably having 1 to 12 carbon atoms and still morepreferably having 1 to 8 carbon atoms, and examples of an alkyl groupinclude: a methyl group, an ethyl group, an iso-propyl group, atert-butyl group, an n-octyl group, an n-decyl group, an n-hexadecylgroup, a cyclopropyl group, a cyclopentyl group and a cyclohexyl group);an alkenyl group (preferably having 2 to 20 carbon atoms, morepreferably having 2 to 12 carbon atoms and specifically preferablyhaving 2 to 8 carbon atoms, and examples of the alkenyl group include: avinyl group, an allyl group, a 2-butenyl group and 3-pentenyl group); analkynyl group (preferably having 2 to 20 carbon atoms, more preferablyhaving 2 to 12 carbon atoms and specifically preferably having 2 to 8carbon atoms, and examples of the alkynyl group include: a propargylgroup and a 3-pentynyl group); an aryl group (preferably having 6 to 30carbon atoms, more preferably having 6 to 20 carbon atoms andspecifically preferably having 6 to 12 carbon atoms, and examples of thearyl group include: a phenyl group, a p-methylphenyl group and anaphthyl group); a substituted or unsubstituted amino group (preferablyhaving 0 to 20 carbon atoms, more preferably having 0 to 10 carbon atomsand specifically preferably having 0 to 6 carbon atoms, and examples ofthe amino group include: an amino group, a methylamino group, adimethylamino group, a diethylamino group and a dibenzylamino group); analkoxy goup (preferably having 1 to 20 carbon atoms, more preferablyhaving 1 to 12 carbon atoms and specifically preferably having 1 to 8carbon atoms, and examples of the alkoxy group include: a methoxy group,an ethoxy group and a butoxy group); an aryloxy group (preferably having1 to 20 carbon atoms, more preferably having 1 to 12 carbon atoms andspecifically preferably having 1 to 8 carbon atoms, and examples of thearyloxy group include: a phenyloxy group and a 2-naphthyloxy group); anacyl group (preferably having 1 to 20 carbon atoms, more preferablyhaving 1 to 16 carbon atoms and specifically preferably having 1 to 12carbon atoms, and examples of the, acyl group include: an acetyl group,a benzoyl group, a formyl group and a pivaloyl group); an alkoxycarbonylgroup (preferably having 2 to 20 carbon atoms, more preferably having 2to 16 carbon atoms and specifically preferably having 2 to 12 carbonatoms, and examples of the alkoxycarbonyl group include: amethoxycarbonyl group and an ethoxycarbonyl group); an aryloxycarbonylgroup (preferably having 7 to 20 carbon atoms, more preferably having 7to 16 carbon atoms and specifically preferably having 7 to 10 carbonatoms, and a phenyloxycarbonyl group is cited as an example of thealkoxycarbonyl group); an acyloxy group (preferably having 2 to 20carbon atoms, more preferably having 2 to 16 carbon atoms andspecifically preferably having 2 to 10 carbon atoms, and examples of theacyloxy group include: an acetoxy group and a benzoyloxy group); anacylamino group (preferably having 2 to 20 carbon atoms, more preferablyhaving 2 to 16 carbon atoms and specifically preferably having 2 to 10carbon atoms, and examples of the acylamino group include: anacetylamino group and a benzoylamino group); an alkoxycarbonylaminogroup (preferably having 2 to 20 carbon atoms, more preferably having 2to 16 carbon atoms and specifically preferably having 2 to 12 carbonatoms, and examples of the alkoxycarbonylamino group include: amethoxycarbonylamino group); an aryloxycarbonylamino group (preferablyhaving 7 to 20 carbon atoms, more preferably having 7 to 16 carbon atomsand specifically preferably having 1 to 12 carbon atoms, and examples ofthe aryloxycarbonylamino group include: a phenyloxycarbonylamino group);a sulfonylamino group (preferably having 1 to 20 carbon atoms, morepreferably having 1 to 16 carbon atoms and specifically preferablyhaving 1 to 2 carbon atoms, and examples of the sulfonylamino groupinclude: a methanesulfonylamino group and a benzensulfonylamino group);a sulfamoyl group (preferably having 0 to 20 carbon atoms, morepreferably having 0 to 16 carbon atoms and specifically preferablyhaving 0 to 12 carbon atoms, and examples of the sulfamoyl groupinclude: a sulfamoyl group, a methylsulfamoyl group, a dimethylsulfamoylgroup and a phenylsulfamoyl group); a carbamoyl group (preferably having1 to 20 carbon atoms, more preferably having 1 to 16 carbon atoms andspecifically preferably having 1 to 12 carbon atoms, and examples of thecarbamoyl group include: a carbamoyl group, a methylcarbamoyl group, adiethylcarbamoyl group and a phenylcarbamoyl group); an alkylthio group(preferably having 1 to 20 carbon atoms, more preferably having 1 to 16carbon atoms and specifically preferably having 1 to 12 carbon atoms,and examples of the alkoxy group include: a methylthio group and anethylthio group); an arylthio group (preferably having 6 to 20 carbonatoms, more preferably having 6 to 16 carbon atoms and specificallypreferably having 6 to 12 carbon atoms, and examples of the arylthiogroup include: a phenylthio group); a sulfonyl group (preferably having1 to 20 carbon atoms, more preferably having 1 to 16 carbon atoms andspecifically preferably having 1 to 12 carbon atoms, and examples of thesulfonyl group include: a mesyl group and a tosyl group); a sulfinylgroup (preferably having 1 to 20 carbon atoms, more preferably having 1to 16 carbon atoms and specifically preferably having 1 to 12 carbonatoms, and examples of the sulfinyl group include: a methanesulfinylgroup and a benzenesulfinyl group); an ureido group (preferably having 1to 20 carbon atoms, more preferably having 1 to 16 carbon atoms andspecifically preferably having 1 to 12 carbon atoms, and examples of theureido group include: an ureido group, a methylureido group and aphenylureido group); a phosphoric acid amide group (preferably having 1to 20 carbon atoms, more preferably having 1 to 16 carbon atoms andspecifically preferably having 1 to 12 carbon atoms, and examples of thephosphoric acid amide group include: a diethyl phosphoric acid amidegroup and a phenyl phosphoric acid amide group);

a hydroxy group; a sulfhydryl group; a halogen atom (for example, afluorine atom and a chlorine atom, a bromine atom and an iodine atom); acyano group; a sulfo group; a carboxyl group; a nitro group; ahydroxamic acid group; a sulfino group; a hydrazino group; an iminogroup; a heterocycle group (preferably having 1 to 30 carbon atoms andmore preferably having 1 to 12 carbon atoms, and examples of a heteroatom include: a nitrogen atom, an oxygen atom and a sulfur atom, andconcrete examples include: an imidazolyl group, a pyridyl group, aquinolyl group, a furyl group, a piperidyl group, a morpholino group, abenzoxazolyl group, a benzimidazolyl group and a benzthiazolyl group);and a silyl group (preferably having 3 to 40 carbon atoms, morepreferably having 3 to 30 carbon atoms and specifically preferablyhaving 3 to 24 carbon atoms, and examples of the silyl group include: atrimethylsilyl group and a triphenylsilyl group). These substituents mayfurther be substituted, and, when two or more substituents are included,they may be the same or different. Further, the substituents may becombined to form a ring.

X¹ and X² each represent a hydrogen atom or a substituent, and at leastone of them represents a cyano group, a carbonyl group, a sulfonyl groupor an aromatic heterocycle group. Examples of X¹ and X² include theabove-mentioned substituent T. The substituents X¹ and X² may further besubstituted with other substituent, and, if possible, may be combined toform a condensed ring.

As X¹ and X², preferable are: a hydrogen atom, an alkyl group, an arylgroup, a cyano group, a nitro group, a carbonyl group, a sulfonyl groupand an aromatic heterocycle group; more preferable are: a cyano group, acarbonyl group, a sulfonyl group and an aromatic heterocycle group;still more preferable are: a cyano group and a carbonyl group; andspecifically preferable are: a cyano group and an alkoxycarbonyl group(—C(═O)OR (R represents an alkyl group having 1-20 carbon atoms, an arylgroup having 6-12 carbon atoms or combination thereof)).

Preferable as Formula (17) includes a compound represented by Formula(18).

(in the formula, R¹ R² R³ , R⁴, R⁵, R⁶, R⁷, R⁸, R⁹ and R¹⁰ eachindependently represent a hydrogen atom or a substituent, X¹ and X² arecommon to X¹ and X² in Formula (17) and the preferable range is alsocommon) independently among a formula, respectively.)

R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸, R⁹ and R¹⁰ each independently representa hydrogen atom or a substituent and examples thereof include theabove-mentioned substituent T. These substituents may further besubstituted with other substituent. These substituents may be fused eachother to form a ring.

As R¹, R², R⁴, R⁵, R⁶, R⁷, R⁹ and R¹⁰ , preferable are: a hydrogen atom,an alkyl group, an alkenyl group, an alkynyl group, an aryl group, asubstituted or unsubstituted amino group, an alkoxy group, an aryloxygroup, a hydroxy group and a halogen atom; more preferable are: ahydrogen atom, an alkyl group, an aryl group, an alkyloxy group, anaryloxy group and a halogen atom; still more preferable are: a hydrogenatom and an alkyl group having 1-12 carbon atoms; specificallypreferable are: a hydrogen atom and a methyl group; and most preferableis a hydrogen atom.

As R³ and R⁸, preferable are: a hydrogen atom, an alkyl group, analkenyl group, an alkynyl group, an aryl group, a substituted orunsubstituted amino group, an alkoxy group, an aryloxy group, a hydroxygroup and a halogen atom; more preferable are: a hydrogen atom, an alkylgroup having 1-20 carbon atoms, an amino group having 0-20 carbon atoms,an alkoxy group having 1-12 carbon atoms, an aryloxy group having 6-12carbon atoms and a halogen atom; still more preferable are: a hydrogenatom and an alkyl group having 1-12 carbon atoms and an alkoxy grouphaving 1-12 carbon atoms; and specifically preferable is a hydrogenatom.

Preferable as Formula (17) includes a compound represented by Formula(19).

(in the formula, R³ and R⁸ are common to R³ and R⁸ in Formula (17) andthe preferable range is also common, and X³ represents a hydrogen atomor a substituent)

X³ represents a hydrogen atom or a substituent and examples thereofinclude the above-mentioned substituent T. As X³, preferable are: ahydrogen atom, an alkyl group, an aryl group, a cyano group, a nitrogroup, a carbonyl group, a sulfonyl group and an aromatic heterocyclegroup; more preferable are: a cyano group, a carbonyl group, a sulfonylgroup and an aromatic heterocycle group; still more preferable are: acyano group and a carbonyl group; and specifically preferable are: acyano group and an alkoxycarbonyl group (—C(═O)OR (R represents an alkylgroup having 1-20 carbon atoms, an aryl group having 6-12 carbon atomsor combination thereof)).

Preferable as Formula (17) includes a compound represented by Formula(20).

(in the formula, R³ and R⁸ are common to R³ and R⁸ in Formula (18) andthe preferable range is also common, and R²¹ represents an alkyl grouphaving 1 to 20 carbon atoms)

When both R³ and R⁸ each are a hydrogen atom, preferable as R21 is analkyl group having 2 to 12 carbon atoms, more preferable is an alkylgroup having 4 to 12 carbon atoms, still more preferable is an alkylgroup having 6 to 12 carbon atoms, specifically preferable is an n-octylgroup, a tert-octyl group, a 2-ethylhexyl group, an n-decyl group or ann-dodecyl group, and most preferable is a 2-ethylhexyl group.

When R³ and R⁸ each are a group other than a hydrogen atom, preferableas R²¹ is an alkyl group having a molecular weight of not less than 300and having not more than 20 carbon atoms.

A compound represented by Formula (17) can be prepared according to themethod described in Journal of American Chemical Society, Vol. 63, p3452 (1941).

Examples of a compound represented by Formula (17) will be shown below,however, the present invention is not limited thereto.

These compounds can be incorporated with the content of 0.1-15 wt % inthe cellulose ester film of the present invention.

(Cellulose Ester)

The cellulose ester employed in the present invention is preferably alower fatty acid ester of cellulose. The lower fatty acids in lowerfatty acid esters of cellulose, as described herein, refers to fattyacids having at most 6 carbon atoms. It is possible to employ, forexample, cellulose acetate, cellulose propionate, and cellulosebutyrate, as well as mixed fatty acid esters such as cellulose acetatepropionate or cellulose acetate butyrate, described in JP-A Nos.10-45804 and 8-231761 and U.S. Pa. No. 2,319,052. Of the above, lowerfatty acid esters, which are particularly preferred, are cellulosetriacetate and acetate propionate. These cellulose esters may beemployed individually or in combinations.

In the case of cellulose triacetate, one at an average degree ofacetylation (the amount of bonded acetic acid) of 54.0-62.5% ispreferably employed, but one at an average degree of acetification of58.0-62.5 is more preferred.

Preferred cellulose esters other than cellulose triacetate are thosewhich simultaneously satisfy following Formulas (I) and (II), providedthat X represents the degree of substitution by an acetyl group and Yrepresents degree of substitution by a fatty acid ester having 3-22carbon atoms. Specifically preferable is a cellulose ester in which Ycontains a propionyl group or a butyryl group.2.8≦X+Y≦3.0   (I)1.0≦X≦2.95   (II)wherein X represents the degree of substitution by an acetyl group, andY represents the degree of substitution by a fatty acid ester grouphaving 3-22 carbon atoms.

Glucose units under β-1,4 bond, which constitute cellulose, incorporatea free hydroxyl group at positions 2, 3, and 6. Cellulose acylate is apolymer in which some or all of these hydroxyl groups are substitutedwith an acyl group (namely, being esterified). The degree (the degree ofsubstitution is 1 for 100% esterification) of acyl substitution refersto the ratio of esterification of cellulose at each of positions 2, 3and 6. Further, when the hydroxyl groups at positions 2, 3 and 6 aresubstituted with Y, the ratio is at least 28%. However, the above ratiois preferably at least 30% of the whole hydroxyl groups, is morepreferably 31%, but is most preferably at least 32%.

Further, a cellulose acylated film is also preferred in which the totaldegree of substitution of X and Y at position 6 of cellulose acylate iscommonly at least 0.8, is preferably 0.85, but is more preferably 0.90.

Synthesis of these cellulose acrylates which exhibit a large degree ofsubstitution at position 6 is described in JP-A Nos. 11-5851,20002-212338, and 2002-338601.

Acyl groups having 3-22 carbon atoms of the cellulose acylate of thepresent invention may be either an aliphatic group or an aryl group, andare not particularly limited. Examples include alkylcarbonyl ester,alkenylcarbonyl ester, aromatic carbonyl ester and aromaticalkylcarbonyl ester of cellulose, each of which may further incorporatea substituted group. Cited as preferred groups may be propionyl,butanoyl, heptanoyl, hexanoyl, octanoyl, decanoyl, dodecanoyl,tridecanoyl, tetradecanoyl, hexadecanoyl, octadecanoyl, iso-butanoyl,t-butanoyl, cyclohexanecarbonyl, oleoyl, benzoyl, naphthylcarbonyl, andcinnamoyl groups. Of these, preferred are propionyl, butanoyl,dodecanoyl, octadecanoyl, t-butanoyl, oleoyl, benzoyl, naphthylcarbonyl,and cinnamoyl groups.

Further, of these, preferred is cellulose acetate propionate, whichsatisfies 0≦X≦2.95 and 0.1≦Y≦2.0. Any portion which is not substitutedwith an acyl group is commonly present as a hydroxyl group. These aresynthesized by methods known in the art.

Cellulose esters, which are synthesized employing, as a raw material,cotton linter, wood pulp, or kenaf, may be employed individually or incombinations. Specifically, it is preferable that cellulose esterssynthesized employing cotton linter (hereinafter also referred to simplyas linter) are employed individually or in combinations.

As the molecular weight of cellulose ester increases, the variationratio of the elastic modulus, due to heat, decreases. When the molecularweight increases excessively, the viscosity of the resultant celluloseester-dissolved solution increases excessively, whereby productivity isdegraded. The molecular weight of cellulose esters is preferably30,000-200,000 in terms of number average molecular weight (Mn), but ismore preferably 40,000-170,000.

Cellulose esters preferably exhibit the following characteristics. When1 g of cellulose ester is charged into 20 ml of pure water (at anelectric conductivity of at most 1 μs/cm and a pH of 6.8) and theresulting mixture is stirred at 25° C. for one hour under a nitrogenatmosphere, the resulting pH and electric conductivity are preferably6-7 and 1-100 μS/cm, respectively. When the pH is less than 6, thedegradation of cellulose tends to be accelerated by residual organicacids during heat-melting. When the pH is at least 7, hydrolysis may beaccelerated. Further, an electric conductivity of at least 100 μS/cm isconsidered to be a factor to degrade cellulose during heating due to thepresence of a relatively large amount of residual ions.

(Plasticizer)

In the dope used for forming the cellulose ester film of the presentinvention, a plasticizer, an ultraviolet (UV) absorber or an antioxidantmay be incorporated. These additives are preferably incorporated so asnot to nortably increase the Rt value.

In the cellulose ester film of the present invention, the followingplasticizers are applicable.

Phosphate ester plasticizer: Specific examples of the phosphate esterplasticizer include phosphoric acid alkyl esters such as triacetylphosphate and tributyl phosphate; phosphoric acid cycloalkyl esters suchas tricyclopentyl phosphate and cyclohexyl phosphate; and phosphoricacid aryl esters such as triphenyl phosphate, tricresyl phosphate,cresylphenyl phosphate, octyldiphenyl phosphate, diphenylbiphenylphosphate, trioctyl phosphate, tributyl phosphate, trinaphtyl phosphate,trixylyl phosphate, trisortho-biphenyl phosphate. The substituent groupsfor these may be the same or different, and may be further substituted.The substituent groups may be a mix of an alkyl group, a cycloalkylgroup and an aryl group, and the substituent groups may be bonded toeach other via covalent bond.

Examples of the phosphoric acid ester also include phosphate esters, forexample: alkylenebis(dialkylphosphate) such asethylenebis(dimethylphosphate) or butylenebis(diethylphosphate);alkylenebis(diarylphosphate) such as ethylenebis(diphenylphosphate) orpropylenebis(dinaphtylphosphate); arylenebis(dialkylphosphate) such asphenylenebis(dibutylphosphate) or biphenylenebis(dioctylphosphate); andarylenebis(diarylphosphates) such as phenylenebis(diphenylphosphate) ornaphtylenebis (ditriylphosphate). These substituent groups may be thesame or different, and may be further substituted. The substituentgroups may be a mixture of an alkyl group, cycloalkyl groups and arylgroups, and the substituent groups may be bonded to each other viacovalent bond.

Furthermore, a part of the structure of the phosphate ester may be apart of the polymer or may be systematically included as a pendant. Itmay also be introduced into a part of the molecular structure of theadditive such as the antioxidant, the acid scavenger, the ultravioletlight absorber. Of the compounds listed above, aryl phosphate ester andarylenebis(diarylphosphate) are preferable, and more specifically,triphenyl phosphate and phenylenebis(diphenylphosphate) are preferable.

Ethylene glycol ester plasticizer: Specific examples of an ethyleneglycol ester plasticizer include: ethylene glycol alkyl esterplasticizers such as ethylene glycol diacetate and ethylene glycoldibutyrate; ethylene glycol cycloalkyl ester plasticizers such asethylene glycol dicyclopropyl carboxylate and ethylene glycoldicyclohexyl carboxylate; and ethylene glycol aryl ester plasticizerssuch as ethylene glycol dibenzoate and ethylene glycol di-4-methylbenzoate. These alkylate groups, cycloalkylate groups and arylate groupsmay be the same or different and may further be substituted. Thesubstituent groups may be a mixture of alkylate groups, cycloalkylategroups and arylate groups, and the substituent groups may be bonded toeach other via covalent linkage. Further, the ethylene glycol portionsmay be substituted and the ethylene glycol ester part of the structuremay be part of the polymer or may be systematically included as apendant. It may also be introduced into a part of the molecularstructure of the additives such as an antioxidant, an acid scavenger,and an ultraviolet light absorber.

Glycerin ester plasticizers: Examples of a glycerin ester plasticizerinclude: glycerin alky esters such as triacetin, tributylin, glycerindiacetate caprylate and glycerin oleate propionate; glycerin cycloalkylesters such as glycerin tricyclopropyl carboxylate, and glycerintricyclohexyl carboxylate; glycerin aryl esters such as glycerintribenzoate and glycerin 4-methylbenzoate; diglycerin alkyl esters suchas diglycerin tetraacetylate, diglycerin tetrapropionate, digylcerinacetate tri caprylate and diglycerin tetralaurate; diglycerin cycloalkylesters such as diglycerin tetracylobutyl carboxylate and diglycerintetracylopentyl carboxylate; and diglycerin aryl esters such asdiglycerin tetrabenzoate and diglycerin 3-methyl benzoate. Thesealkylate groups, cycloalkyl carboxylate groups and arylate groups may besame or different and may further be substituted. The substituent groupsmay be a mixture of an alkylate group, a cycloalky carboxylate group andan arylate groups, and the substituent groups may be bonded to eachother via covalent bond. Further, the glycerin and diglycerin portionsmay be substituted and a partial structure of the glycerin ester ordiglycerin ester may be a part of the polymer or may be systematicallyincluded as a pendant. It may also be introduced into a part of themolecular structure of the additive such as an antioxidant, an acidscavenger, and an ultraviolet light absorber.

Polyalcohol ester plasticizers: Specific examples of polyalcohol esterplasticizers include the polyalcohol ester plasticizers disclosed inJP-A 2003-12823, paragraphs 30-33.

These alkylate groups, cycloalkyl carboxylate groups and arylate groupsmay be the same or different and may be further be substituted. Thealkylate groups, cycloalky carboxylate groups and arylate groups may bemixed, and the substituent groups may be bonded to each other viacovalent bond. Furthermore, the polyhydric alcohol portion may besubstituted and a partial structure of the polyhydric alcohol may be apart of the polymer or may be systematically included as a pendant. Itmay also be introduced into a part of the molecular structure of theadditives such as an antioxidant, an acid scavenger or an ultravioletlight absorber.

Dicarboxylic acid ester plasticizer: Specific examples of a dicarboxylicacid ester plasticizer include: alkyl dicarboxylic acid cycloalkyl esterplasticizers such as didodecyl malonate (C1), dioctyl adipate (C4) anddibutyl cebacate (C8); alkyl dicarboxylic acid cycloalkyl esterplasticizers such as dicyclopentyl succinate and dicyclohexyl adipate;alkyl dicarboxylic acid aryl ester plasticizers such as diphenylsuccinate and di-4-methyl phenyl glutarate; cycloalkyl dicarboxylic acidalkyl ester plasticizers such as dihexyl-1,4-cyclohexane dicarboxylateand didecyl bicyclo [2.2.1]heptane-2,3-dicarboxylate; cycloalkyldicarboxylic acid cycloalkyl ester plasticizers such asdicyclohexyl-1,2-cyclobutane dicarboxylate anddicyclopropyl-1,2-cyclohexyl dicarboxylate; cycloalkyl dicarboxylic acidaryl ester plasticizers such as diphenyl-1,1-cyclopropyl dicarboxylateand di-2-naphthyl-1,4-cyclohexane dicarboxylate; aryl dicarboxylic acidalkyl ester plasticizers such as diethyl phthalate, dimethyl phthalate,dioctyl phthalate, dibutyl phthalate and di-2-ethylhexyl phthalate; aryldicarboxylic acid cycloalkyl ester plasticizers such as dicyclopropylphthalate and dicyclohexyl phthalate; and aryl dicarboxylic acid arylester plasticizers such as diphenyl phthalate and di-4-methylphenylphthalate. These alkoxy groups and cycloalkoxy groups may be the same ordifferent, and may also be monosubstituted and the substitution groupsmay be further substituted. The alkyl groups and the cycloalkyl groupsmay be mixed, and the substituent groups may be bonded to each other viacovalent bond. Furthermore, the aromatic ring of the phthalic acid maybe substituted and may be a multimer such as a dimer, a trimer or atetramer. The phthalic acid ester part of the structure may be a part ofthe polymer or may be systematically included as a pendant. It may alsobe introduced into a part of the molecular structure of the additivessuch as an antioxidant, an acid scavenger and an ultraviolet lightabsorber.

Polyhydric carboxylic acid ester plasticizers: Specific examples ofpolyhydric carboxylic acid ester plasticizers include: alkyl polyhydriccarboxylic acid alkyl ester plasticizers such as tridodecyl tricarbalateand tributyl-meso-butane-1,2,3,4,-tetracarboxylate; alkyl polyhydriccarboxylic acid cycloalkyl ester plasticizers such as tricyclohexyltricarbalate and tricyclopopyl-2-hydroxy-1,2,3-propane tricarboxylate;alkyl polyhydric carboxylic acid aryl ester plasticizers such astriphenyl-2-hydroxyl-1,2,3-propane tricarboxylate, tetra-3-methylphenyltetrahydrofuran-2,3,4,5-tetracarboxylate; cycloalkyl polyhydriccarboxylic acid alkyl ester plasticizers such astetrahexyl-1,2,3,4-cyclobutane tetracarboxylate andtetrabutyl-1,2,3,4,-dicyclopentane tetracarboxylate; cycloalkylpolyhydric carboxylic acid cycloalkyl ester plasticizers such astetracyclopropyl-1,2,3,4-cyclobutane tetracarboxylate andtricyclohexyl-1,3,5-cyclohexyl tricarboxylate; cycloalkyl polyhydriccarboxylic acid aryl ester plasticizers such astriphenyl-1,3,5-cyclohexyl tricarboxylate,hexa-4-methylphenyl-1,2,3,4,5,6-cyclohexyl hexacarboxylate; arylpolyhdric carboxylic acid alkyl ester based plasticizers such astridodecyl benzene-1,2,4-tricarboxylate andtetraoctylbenzene-1,2,4,5-tetracarboxylate; aryl polyhdric carboxylicacid cycloalkyl ester plasticizers such as tricyclopentylbenzene-1,3,5-tricarboxylate and tetracyclohexyl benzene-1,2,3,5tetracarboxylate; and aryl polyhdric carboxylic acid aryl esterplasticizers such as triphenyl benzene-1,3,5-tetracarboxylate andhexa-4-methylphenyl benzene-1,2,3,4,5,6-hexacarboxylate. These alkoxygroups and cycloalkoxy groups may be the same or different, and may alsobe substituted and the substitution groups may be further substituted.The alkyl groups and the cycloalkyl groups may be mixed, and thesubstituent groups may be bonded to each other by common bonds.Furthermore, the aromatic ring of the phthalic acid may be substitutedand may be a polymer such as a dimer, trimer, tetramer and the like. Thephthalic acid ester part of the structure may be a part of the polymeror may be systematically included as a pendant. It may also beintroduced into a part of the molecular structure of the additive suchas an antioxidant, an acid scavenger and an ultraviolet light absorber.

(UV Absorber)

The cellulose ester film of the present invention may not contain a UVabsorber, and when UV absorbing property is provided, a UV absorber maybe contained. A UV absorber has a role to prevent deterioration ofliquid crystals or a polarizing film when used outdoor, however, whenthe cellulose ester film of the present invention is used between apolarizing film and a liquid crystal cell as a polarizing plateprotective film, a UV absorber may not be incorporated in order to have,for example, a higher transmittance of visible rays.

A UV absorber preferably has an excellent ability to absorb UV rays ofwhich wavelength is not more than 370 nm, while the absorbance forvisible rays with a wavelength of 400 nm or more is as small aspossible, and the transmittance is preferably 50% or more. Specifically,the transmittance at the wavelength of 370 nm is preferably 10% or lessand more preferably 5% or less. Examples of a UV absorber usable in thepresent invention include: oxybenzophenone, benzotriazole, salicylateester, benzophenone, cyanoacrylate, triazine and a nickel complex. Ofthese, preferable compounds include benzotriazole because of littlecoloring. Examples of preferably usable UV absorber include: TINUVIN109, TINUVIN 171, TINUVIN 326, TINUVIN 327 and TINUVIN 328 produced byCiba Specialty Chemicals Inc. Since a low molecular weight UV absorbertends to deposit on the web or evaporate while the film is produced,like a plasticizer, the content is preferably 1-10% by weight.

In the present invention, a polymer UV absorber is preferablyincorporated in the cellulose ester film since the polymer UV absorberis more difficult to deposit than the above mentioned low molecularweight UV absorber, whereby UV rays are thoroughly blocked withoutlosing dimensional stability, retention of the UV absorber,anti-permeability, while preventing phase separation of the UV absorberin the film. As a polymer UV absorber usable in the present invention,the polymer UV absorbers disclosed in JP-A No. 6-148430 and polymerscontaining a UV absorbing monomer can be used without limitation.

It is preferable in the present invention that a UV absorbing copolymer(also referred to as a polymer UV absorber) obtained from a UV absorbingmonomer represented by Formula (21) is incorporated in the celluloseester film.

(in the formula, n represents an integer of 0-3, R₁—R₅ each represent ahydrogen atom, a halogen atom or a substituent, X represents —COO—,CONR₇—, —OCO— or —NR₇CO—, R₆ and R₇ each represent a hydrogen atom, analkyl group or an aryl group, provided that the group represented by R₆contains a polymerizable group as a substructure)

In Formula (21), n represents an integer of 0-3, and when n is 2 ormore, plural R₅ may be the same or different to each other and may becombined to form a 5-7 membered ring.

R₁—R₅ each represent a hydrogen atom, a halogen atom or a substituent.Examples of a halogen atom include: a fluorine atom, a chlorine atom, abromine atom and an iodine atom. Of these, preferable is a fluorine atomor a chlorine atom. Examples of a substituent include: alkyl groups (forexample, a methyl group, an ethyl group, an isopropyl group, ahydroxyethyl group, a methoxymethyl group, a trifluoromethyl group and at-butyl group), alkenyl groups (for example, a vinyl group, an allylgroup and a 3-butene-1-yl group), aryl groups (for example, a phenylgroup, a naphthyl group, a p-tolyl group and a p-chlorophenyl group),heterocycle groups (for example, a pyridyl group, a benzimidazolylgroup, a benzthiazolyl group and a benzoxazolyl group), alkoxy groups(for example, a methoxy group, an ethoxy group, an isopropoxy group anda n-butoxy group), aryloxy groups, (for example, a phenoxy group),heterocycleoxy groups (for example, a 1-phenyltetrazole-5-oxy group anda 2-tetrahydropyranyloxy group), acyloxy groups (for example, an acetoxygroup, a pivaloyloxy group and a benzoyloxy group), acyl groups (forexample, an acetyl group, a propanoyl group and a butyroyl group),alkoxycarbonyl groups (for example, a methoxycarbonyl group and anethoxycarbonyl group), aryloxycarbonyl groups (for example, aphenoxycarbonyl group), carbamoyl groups (for example, a methylcarbamoylgroup, an ethylcarbamoyl group and a dimethylcarbamoyl group), aminogroups, alkylamino groups (for example, a methylamino group, anethylamino group and a diethylamino group), anilino groups (for example,an anilino group and a N-methylanilino group), acylamino groups (forexample, an acetylamino group and a propionylamino group), a hydroxylgroup, cyano groups, nitro groups, sulfonamide groups (for example, amethanesulfonamide group and a benzenesulfonamide group), sulfamoylaminogroups (for example, a dimethylsulfamoylamino group), sulfonyl groups(for example, a methanesulfonyl group, a butanesulfonyl group and aphenylsulfonyl group), sulfamoyl groups (for example, an ethylsulfamoylgroup and a dimethylsulfamoyl group), sulfonylamino groups (for example,a methanesulfonylamino group and a benzenesulfonylamino group), ureidogroups (for example, a 3-methylureido group, a 3,3-dimethylureido groupand a 1,3-dimethylureido group), imide groups (for example, aphthalimide group), silyl groups (for example, a trimethylsilyl group, atriethylsilyl group and a t-butyldimethylsilyl group), alkylthio groups(for example, a methylthio group, an ethylthio group and an n-butylthiogroup), and arylthio groups (for example, a phenylthio group). Of these,preferable are, for example, alkyl groups and an aryl groups.

In Formula (21), the groups represented by R₁—R₅ each may be furthersubstituted, if possible and neighboring groups of R₁—R₄ may be combinedto form a 5-7 membered ring.

R₆ represents a hydrogen atom, an alkyl group, a cycloalkyl group, analkenyl group or an alkynyl group. Examples of an alkyl group include: amethyl group, an ethyl group, a propyl group, an isopropyl group, ann-butyl group, an isobutyl group, a t-butyl group, an amyl group, anisoamyl group and a hexyl group. The above alkyl groups may further havea halogen atom or a substituent. Examples of a halogen atom include: afluorine atom, a chlorine atom, a bromine atom and an iodine atom.Examples of a substituent include: acyl groups (for example, an acetylgroup, a propanoyl group and a butyroyl group), alkoxy groups (forexample, a methoxy group, an ethoxy group, an isopropoxy group and an-butoxy group), amino groups, alkylamino groups (for example, amethylamino group, an ethylamino group and a diethylamino group),acylamino groups (for example, an acetylamino group and a propionylaminogroup), a hydroxyl group, cyano groups, carbamoyl groups (for example, amethylcarbamoyl group, an ethylcarbamoyl group and a dimethylcarbamoylgroup), acyloxy groups (for example, an acetoxy group and a pivaloyloxygroup) and alkoxycarbonyl groups (for example, a methoxycarbonyl groupand an ethoxycarbonyl group).

Examples of a cycloalkyl group include: saturated cyclohydrocarbongroups such as a cyclopentyl group, a cyclohexyl group, a norbornylgroup and an adamantyl group, which may be further substituted or maynot be substituted.

Examples of an alkenyl group include: a vinyl group, an allyl group,1-methyl-2-propenyl group, a 3-butenyl group, a 3-methyl-2 butenyl groupand an oleyl group. Of these, preferable are a vinyl group or a1-methyl-2-propenyl group.

Examples of an alkynyl group include: an ethynyl group, a butadiylgroup, a propargyl group, a 1-methyl-2-propynyl group, a 2-butyny group,a 1,1-dimethyl-2-propynyl group. Of these, preferable are, for example,an ethynyl group and a propargyl group.

R₇ represents a hydrogen atom, an alkyl group and a cycloalkyl group.Examples of an alkyl group include: a methyl group, an ethyl group, apropyl group, an isopropyl group, a n-butyl group, an isobutyl group, at-butyl group, an amyl group, an isoamyl group and a hexyl group. Eachof these alkyl groups may further have a halogen atom or a substituent.Examples of a halogen atom include: a fluorine atom, a chlorine atom, abromine atom and an iodine atom. Examples of a substituent include: acylgroups (for example, an acetyl group, a propanoyl group and a butyroylgroup), alkoxy groups (for example, a methoxy group, an ethoxy group, anisopropoxy group and a n-butoxy group), amino groups, alkylamino groups(for example, a methylamino group, an ethylamino group and adiethylamino group), anilino groups (for example, an anilino group andan N-methyl anilino group), acylamino groups (for example, anacetylamino group and a propionylamino group), a hydroxyl group, cyanogroups, carbamoyl groups (for example, a methylcarbamoyl group, anethylcarbamoyl group and a dimethylcarbamoyl group), acyloxy groups (forexample, an acetoxy group and a pivaloyloxy group) and alkoxycarbonylgroups (for example, a methoxycarbonyl group and an ethoxycarbonylgroup).

Examples of a cycloalkyl group include saturated cyclic hydrocarbons,such as a cyclopentyl group, a cyclohexyl group, a norbornyl group, andan adamantyl group, which may be further substituted or may not besubstituted.

In the present invention, the polymerizable group includes anunsaturated ethylenic polymerizable group or a bifunctionalcondensation-polymerizable group, and preferably an unsaturatedethylenic polymerizable group. Concrete examples of the unsaturatedethylenic polymerizable group include a vinyl group, an allyl group, anacryloyl group, a methacryloyl group, a styryl group, an acrylamidogroup, a methacrylamido group, a vinyl cyanide group, a 2-cyanoacryloxygroup, a 1,2-epoxy group and a vinyl ether group and preferably thevinyl group, the acryloyl group, the methacryloyl group, the acrylamidogroup and the methacrylamido group. To have a polymerizable group as asubstructure means that the polymerizable groups are bonded directly orthrough a linking group of divalent or more. Examples of a linking groupof divalent or more include: alkylene groups (such as a methylene group,a 1,2-ethylene group, a 1,3-propylene group, a 1,4-butylene group and acyclohexane-1,4-diyl group); alkenylene groups (such as anethene-1,2-diyl group and a butadiene-1,4-diyl group); alkynylene groups(such as an ethyne-1,2-diyl group, a butane-1,3-diyl-1,4-diyl); andhetero atom linking groups (an oxygen atom, a sulfur atom, a nitrogenatom, a silicon atom and a phosphor atom). Of these, preferable are, forexample, an alkylene group and a hetero atom linking group. These groupsmay be combined to form a composite bonding group. The weight averagemolecular weight of the polymer derived from the UV absorbing monomer is2,000-30,000, and preferably 5,000-20,000.

The weight average molecular weight of the UV absorbing copolymer can becontrolled by known molecular weight controlling methods. Forcontrolling the molecular weight, for example, a method can be appliedin which a chain transfer agent such as carbon terachloride,laurylmercptane or octyl thioglycolate is employed. The polymerizationis usually performed at a temperature of from a room temperature to 130°C., and preferably 50-100° C.

The UV absorbing polymer employed in the present invention may be ahomopolymer derived from a UV absorbing monomer or may be a copolymerderived from the UV absorbing monomer and another polymerizable monomer.Examples of the other monomer capable of polymerizing includeunsaturated compounds, for example, styrene derivatives (such asstyrene, α-methylstyrene, o-methylstyrene, m-methylstyrene,p-methylstyrene and vinylnephthalene); acrylate derivatives (such asmethyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate,i-butyl acrylate, t-butyl acrylate, octyl acrylate, cyclohexyl acrylateand benzyl acrylate); methacrylate derivatives (such as methylmethacrylate, ethyl methacrylate, propyl methacrylate, butylmethacrylate, i-butyl methacrylate, t-butyl methacrylate, octylmethacrylate and cyclohexyl methacrylate); alkyl vinyl ethers (such asmethyl vinyl ether, ethyl vinyl ether and butyl vinyl ether); alkylvinyl esters (such as vinyl formate, vinyl acetate, vinyl butyrate,vinyl capronate and vinyl stearate); crotonic acid; maleic acid; fumaricacid; itaconic acid; acrylonitrile; methacrylonitrile; vinyl chloride;vinylidene chloride; acrylamide; and methacrylamide. Of these, forexample, methyl acrylate, methyl methacrylate and vinyl acetate arepreferred.

It is also preferable that the component other than the UV absorbingmonomer in the polymer derived from the UV absorbing monomer contains ahydrophilic ethylenically unsaturated monomer.

As the hydrophilic ethylenically unsaturated monomer, a hydrophiliccompound having a polymerizable unsaturated double bond in the molecularthereof is employable without any limitation. For example, a unsaturatedcarboxylic acid such as acrylic acid and methacrylic acid, an acrylateand methacrylate each having a hydroxyl group or an ether bond such as2-hydroxyethyl methaceylate, 2-hydroxypropyl methacrylate,tetrahydrfurfuryl methacrylate, 2-hydroxyethyl acrylate, 2-ydroxypropylacrylate, 2,3-dihydroxy-2-methylpropyl methacrylate, tetrahydrofurfurylacrylate, 2-ethoxyethyl acrylate, diethylene glycol ethoxylate acrylateand 3-methoxybutylbutyl acrylate, acrylamide, an N-substituted(meth)acrylamido such as N,N-dimethyl(meth)acrylate, N-vinylpyrrolidoneand N-vinyloxazolidone are employable.

As the hydrophilic ethylenically unsaturated monomer, a (meth)acrylatehaving a hydroxyl group or a carboxyl group in the molecule thereof ispreferable, and 2-hydroxyethyl methacrylate, 2-hydroxypropylmethacrylate, 2-hydroxyethyl acrylate and 2-hydroxypropyl acrylate areparticularly preferable.

These polymerizable monomers can be copolymerized solely or incombination of two or more kinds together with the UV absorbing monomer.

In the present invention, the method for polymerizing the UV absorbingcopolymer is not specifically limited and known methods such as radicalpolymerization, anion polymerization and cation polymerization can bewidely applied. As the initiator for the radical polymerization, an azocompound and a peroxide compound such as azobisisobutylnitrile (AIBN), adiester of azobisisobutylic acid, benzoyl peroxide and hydrogen peroxideare employable. The solvent for polymerization is not specificallylimited, and examples of usable solvent include an aromatic hydrocarbontype solvent such as toluene and chlorobenzene, a halogenizedhydrocarbon type solvent such as dichloroethane and chloroform, a anether type solvent such as tetrahydrofuran and dioxane, an amide typesolvent such as dimethylformamide, an alcohol type solvent such asmethanol, an ester type solvent such as methyl acetate and ethylacetate, a ketone type solvent such as acetone, cyclohexanone and methylethyl ketone, and an aqueous solvent. Solution polymerization in whichthe polymerization is carried out in a uniform system, precipitationpolymerization in which the formed polymer is precipitated, emulsionpolymerization in which the polymerization is carried out in a micellestate and suspension polymerization carried out in a suspended state canbe performed according to selection of the solvent. However, UVabsorbing latex obtained via emulsion polymerization is not preferableto be used as an optical film.

The mixing ratio of the UV absorbing monomer, the polymerizable monomercapable of polymerizing with the UV absorbing monomer and thehydrophilic ethylenically unsaturated monomer is suitably determinedconsidering the compatibility of the obtained UV absorbing copolymerwith the other transparent polymer and the influence on the transparencyand the mechanical strength of the optical compensating film.

The content of the UV absorbing monomer in the polymer derived from theUV absorbing monomer is preferably 1-70%, and more preferably 5-60%, byweight. When the content of the UV absorbent monomer in the UV absorbingpolymer is less than 1%, addition of a large amount of the UV absorbingpolymer is necessary for satisfying the desired UV absorbing ability sothat increasing in the haze or lowering in the transparency and themechanical strength by the precipitation is caused. On the other hand,when the content of the UV absorbing monomer in the UV absorbing polymerexceeds 70% by weight, the transparent optical compensating film isdifficultly obtained sometimes since the compatibility of the polymerwith another polymer is lowered. Also, the workability in the filmforming process and productivity are reduced due to the decrease insolubility in the solvent.

The hydrophilic ethylenically unsaturated monomer is preferablycontained in the UV absorbing copolymer in a ratio of from 0.1 to 50% byweight. When the content is less than 0.1%, the improvement effect onthe compatibility of the hydrophilic ethylenically unsaturated monomercannot be obtained and when the content is more than 50% by weight, theisolation and purification of the copolymer becomes impossible. Morepreferable content of the hydrophilic ethylenically unsaturated monomeris from 0.5 to 20% by weight. When the hydrophilic group is substitutedto the UV absorbing monomer itself, it is preferable that the totalcontent of the hydrophilic UV absorbing monomer and the hydrophilicethylenically unsaturated monomer is within the above-mentioned range.

For satisfying the content of the UV absorbing monomer and thehydrophilic monomer, it is preferable that the an ethylenicallyunsaturated monomer having no hydrophilicity is further copolymerizedadditionally to the above two monomers.

Two or more kinds of each of the UV absorbing monomer and hydrophilic ornon-hydrophilic ethylenically unsaturated monomer may be mixed andcopolymerized.

Typical examples of the UV absorbing monomer to be preferably employedin the present invention are listed below, but the monomer is notlimited thereto.

The UV absorbents, UV absorbing monomers and their intermediates to beemployed in the present invention can be synthesized by referringpublished documents. For example U.S. Pat. Nos. 3,072,585, 3,159,646,3,399,173, 3,761,373, 4,028,331 and 5,683,861, European Patent No.86,300,416, JP-A Nos. 63-227575 and 63-185969, “Polymer Bulletin” V. 20(2), 169-176, and “Chemical Abstracts V. 109, No. 191389 can be referredfor synthesizing.

The UV absorbent and the UV absorbing polymer to be used in the presentinvention can be employed together with a low or high molecular weightcompound or an inorganic compound according to necessity on the occasionof mixing with the other transparent polymer. For example, it is one ofpreferable embodiments that the UV absorbent polymer and anotherrelatively low molecular weight UV absorbent are simultaneously mixedwith the other transparent polymer. Moreover, simultaneously mixing ofan additive such as an antioxidant, a plasticizer and a flame retardantis also one of preferable embodiments.

The ultraviolet light absorber and the ultraviolet light absorbingpolymer used in this invention may be added to a cellulose ester film bybeing included in the cellulose ester film or by being coated on thecellulose ester film. In the case of inclusion in the cellulose esterfilm, direct addition and in-line addition are favorable. The in-lineaddition is a method in which the ultraviolet light absorber and theultraviolet light absorbing polymer are dissolved beforehand in anorganic solvent (such as methanol, ethanol, methylene chloride) anddissolved, and then added to the dope composition using an in-line mixeror the like.

The amount of the ultraviolet light absorber and the ultraviolet lightabsorbing polymer used in this invention is not fixed and depends oftype of compound and the conditions for use. However, in the case of theultraviolet light absorber, for 1 m² of optical film, the amount ispreferably in the range of 0.2-3.0 g, more preferably 0.4-2.0 g and0.5-1.5 g is particularly preferable. In the case of the ultravioletlight absorbing polymer, for 1 m² of optical film, it is preferably inthe range of 0.6-9.0 g, more preferably 1.2-6.0 g and even morepreferably 1.5-3.0 g.

From the viewpoint of preventing deterioration of the liquid crystal, asubstance in which absorbance of ultraviolet light having a wavelengthof no more than 380 nm is excellent, and from the viewpoint of favorableliquid crystal display properties a substance with little absorbance ofvisible light below 400 nm is preferable. In this invention, it ispreferable that at a wavelength of 380 nm, transparency is not more than8%, and preferably not more than 4% and transparency of not more than 1%is particularly preferable.

As UV absorbent monomers available on the market,1-(2-bezotriazole)-2-hydroxy-5-(vinyloxycarbonylethyl)-benzene UVM-1 anda reactive type UV absorbent1-(2-benzotriazole)-2-hydroxy-5-(2-methacryloyloxyethyl)-benzeneRUVA-93, each manufactured by Ootsuka Chemical Co., Ltd., and similarcompounds are employable in the present invention. They are preferablyemployed solely or in a state of polymer or copolymer but not limitedthereto. For example, a polymer UV absorbent available on the marketPUVA-30M, manufactured by Ootsuka Chemical Co., Ltd., is preferablyemployed. The UV absorbent may be used in combination of two or morekinds thereof. The method for adding the ultraviolet light absorber tothe dope may be by dissolving the ultraviolet light absorber in anorganic solvent such as alcohol, methyl chloride, dioxolane or methylacetate, and then adding it to the dope, or alternatively theultraviolet light absorber may be directly added to the dopecomposition.

An antioxidant may be included in the cellulose ester film of thisinvention. For example as described in JP-A No. 5-197073, a peroxidedecomposing agent, a radical chain-linking agent, or metal deactivatoror an acid trapping agent may also be included. The amount in whichthese compounds are added is preferably in a weight ratio of 1 ppm-1.0%,and more preferably 10-1,000 ppm to the cellulose ester.

In the present invention, it is preferable that a particle matting agentis included in the cellulose ester film, and examples of the particlematting agent include particles of inorganic compounds such as silicondioxide, titanium dioxide, aluminum oxide, zirconium oxide, calciumcarbonate, kaolin, talc, burned calcium silicate, hydrated calciumsilicate, aluminum silicate, magnesium silicate, and calcium phosphateor cross-linked particles of high molecular weigh polymers Of these,silicon dioxide is preferable in view of reduced haze in the film. Theaverage particle diameter of the secondary particles from among theparticles is preferably in the range of 0.01-1.0 μm and the amount ofthese particles included is preferably in the range of 0.005-0.3 percentby weight of the cellulose ester. The particles such as the silicondioxide particles are often surface treated using an organic substance,and this is preferable because it reduces haze in the film. Examples ofthe organic compound used in the surface treatment include halogens,alkoxysilanes (particularly alkoxysilanes having a methyl group),silazanes, and siloxanes. Particles having a larger average particlediameter have a greater matting effect, while particles having a smalleraverage particle diameter have excellent transparency. Thus among theparticles, the primary particles preferably have an average primaryparticle size of 5-50 nm, and more preferably 7-16 nm. These particlesare usually present in the cellulose ester film as an aggregate, andpreferably form unevenness of 0.01-1.0 μm in the plane of the celluloseester film. Examples of the silicon dioxide particles include Aerosil200, 200V, 300, R972, R972V, R974, R202, R812, OX50, or TT600 (eachmanufactured by Aerosil Co., Ltd.), and of these, Aerosil 200V, R972,R972V, R974, R202, and R812, are preferred. Two or more of these mattingagents may be combined and used. In the case where 2 or more mattingagents are used, they may be mixed in a suitably selected proportion. Inthis case, matting agents which have different particle size and qualitysuch as Aerosil 200V and R927V may be used in weight proportions in therange from 0.1:99.9 to 99.9:0.1

The method to produce the polarizing plate protective film of thepresent invention will now be described. The cellulose ester film of thepresent invention may be prepared via a solvent-casting method or amelt-casting method, however, specifically preferable is asolvent-casting method.

The method for preparing the cellulose ester dope of the presentinvention will be described. Flakes of cellulose ester are stirred intothe dissolution vessel with an organic solvent, which is the main goodsolvent for the cellulose ester, and thereby dissolved and the dope isformed. Examples of the dissolution method include a method which isperformed at normal pressure; a method which is performed below theboiling point of the main solvent; a method which is performed byapplying pressure below the boiling point of the main solvent; a methodwhich is performed by cold dissolution as described in JP-A No. 9-95544,No. 9-95557, or No. 9-95538; and various dissolution methods performedunder high pressure as disclosed in JP-A No. 11-21379. Afterdissolution, the dope is filtered with a filtering material and thendefoamed and sent to the next step. The cellulose ester concentration inthe dope is between 10 and 35 percent by weight, and more preferablybetween 15 and 25 percent. In order to include the polymer useful in thepresent invention in a cellulose ester dope, the polymer is dissolvedbeforehand in an organic solvent and then added to the cellulose esterdope, and the method for addition, such as direct addition and the likeis not limited. In this case the addition is done such that there is nocloudiness or phase separation of the polymer in the dope. The amount tobe added is as described above.

Examples of good solvents of the cellulose ester include organicsolvents such as, methyl acetate, ethyl acetate, amyl acetate, ethylformate, acetone, cyclohexanone, methyl acetoacetata, tetrahydrofuran,1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,4-dioxane,2,2,2-trifluoroethanol, 2,2,3,3-hexafluoro-1-propanol,1,3-difluoro-2-propanol, 1,1,1,3,3,3-hexafluoro-2-methyl-2-propanol,1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1-propanol,nitroethane, 2-pyrrolidone, N-methyl-2-pyrrolidone,1,3-dimethyl-2-imidazolidinone, methylene chloride, and bromopropane. Ofthese, methyl acetate, acetone and methylene chloride are preferablyused. However, there is a tendency for non-chlorine organic solvents tobe more preferable based on recent environmental issues. Lower alcoholssuch as methanol, ethanol, butanol and the like can be favorably usedalong with these organic solvents, since they can improve the solubilityof the cellulose ester in the organic solvent and reduce the viscosityof the dope. Ethanol in particular is favorable because of its lowboiling point and it low toxicity. It is preferable that organic solventused with the dope of the present invention is a mixture of a goodsolvent and a poor solvent for cellulose ester in view of productionefficiency, and a favorable range of proportion for mixing the goodsolvent and the poor solvent is 70-98 percent by weight of the goodsolvent and 2-30 percent by weight of the poor solvent. A good solventin the present invention is defined as a solvent that will dissolve thecellulose ester that is used on its own while a poor solvent is one thatdoes not dissolve the cellulose ester on its own. The poor solvent usedwith the dope of the present invention is not particularly limited, butexamples of the solvent that is preferably used include methanol,ethanol, n-butanol, cyclohexane, acetone, cyclohexanone and the like.Selection of the organic solvent for the polymer used in the presentinvention is also preferably a good solvent for cellulose ester. Asdescribed above, in the case where the low molecular weight plasticizeris used, conventional method for addition may be used and theplasticizer may be added directly to the dope or dissolved in an organicsolvent beforehand and then poured into the dope.

When the various additives described above are added to the celluloseester dope, it is preferable that a solution in which the celluloseester dope and the various additives are dissolved in a small amount ofthe cellulose ester is blended by in-line addition. For example, anin-line mixer such as static mixer SWJ (Toray static in-line mixer,Hi-Mixer, manufactured by Toray Engineering) is preferably used. In thecase where the in-line mixer is used, it is preferably applied to a dopein which the cellulose ester is subjected to concentrated dissolutionunder high pressure and in this case, a specific type of pressurizingcontainer may be used, which is capable of withstanding a prescribedpressure, and which can be heated under pressure and in which stirringcan be performed.

In the present invention, by filtering the cellulose ester dope, foreignmatter, particularly foreign matter that can be mistakenly identified asimages in the liquid crystal image display, are removed. It can be saidthat the quality of the polarizing plate protective film is determinedby this filtration. It is preferable that the absolute filtrationaccuracy of the filtering material used in this filtration is small, butif the absolute filtration accuracy is too small, there is clogging ofthe filtration material is likely to occur, and thus the filteringmaterial must be replaced frequently and this causes the problem ofreduced productivity. As a result, the absolute filtration accuracy offiltering material for the cellulose ester dope of the present inventionis preferably in the range not mote than 0.008 mm, more preferably inthe range of 0.001-0.008 mm, and still more preferably in the range of0.003-0.006 mm. The quality of the filtering material is notparticularly limited, and conventional filtering materials may be used.However, filtering material made from plastic fibers such aspolypropylene, Teflon (registered trademark) and the like or filteringmaterial made of metals such as stainless steel are preferable in theview of the fact that there is no falling out of the fibers. Filtrationof the cellulose ester dope of the present invention can be performedusing conventional methods, but a method in which filtration isperformed while heating under reduced pressure at a temperature which isless that the boiling point of the solvent at atmospheric pressure, andwhich is within a range in which the solvent does not boil is preferredin view of the fact that increase in differential pressure afterfiltration (referred to as filtration pressure hereinafter) is small.The preferable temperature range is 45-120° C., more preferably 45-70°C., and still more preferably 45-55° C. The filtration pressure ispreferably small. The filtration pressure is preferably no greater than1.6×10⁶ Pa, more preferably no greater than 1.2×10⁶ Pa, and still morepreferably, no greater than 1.0×10⁶ Pa. Including an unsubstituted acylgroup or a cellulose ester with a low degree of acetylation in rawmaterial for the cellulose ester, sometimes causes foreign materialobstruction (sometimes called luminance point hereinafter). A polarizerwas placed between two cellulose ester film samples arranged in acrossed state (crossed Nicol state). The luminance point is a phenomenonwhich occurs when light was irradiated from one side and observed fromthe other side using an optical microscope (50 magnification) and if thecellulose ester film is a normal one, light is blocked and there isdarkness and nothing can be seen, while if foreign material is present,light leaks from that area and luminance appears as spots. Actual damagewhen the cellulose ester film is used as a liquid crystal image displayis large to the extent that that the diameter of the luminance point islarge, and the diameter of the luminance point should be no greater than50 μm, preferably no greater than 10 μm, and still more preferably nogreater than 8 μm. It is to be noted that the diameter of the luminancepoint is the diameter that is measured when the luminance point isapproximated to a perfect circle. If the diameter of the luminance pointdefined here is 400/cm² or less, there are no problems in terms ofpractical use, the diameter is preferably 300/cm² or less, and morepreferably 200/cm² or less. In order to reduce the amount and size ofthese luminance spots, it is necessary to properly filter fine foreignmaterial. Also, as described in JP-A No. 2000-137115,. the method inwhich a crushed cellulose ester film which has been formed are addedagain in the proportion of the dope and used as the materials for thecellulose ester and the additives is preferably used as the luminancespots are reduced.

Next, the process for casting the cellulose ester dope on a metalsupport, the drying process for drying on the metal support, and thepeeling process for peeling the web from the metal support will bedescribed. The metal support body is an endless metal belt which canmove infinitely or a rotating metal drum with the surface thereof beinga mirror surface. The casting process is one in which a dope is pumpedto a pressure die through a pressure type metering gear pump, and castfrom the pressure die onto a metal support at a casting position.Another casting process is a doctor blade method in which the thicknessof the cast dope film is adjusted with a blade or a method using reverseroll coater in which the dope thickness of the cast dope is adjustedwith a reverse roller coater rotating reversely. A pressure die ispreferred in view of the fact that the slit shape at the opening portioncan be regulated and the film thickness is readily regulated to beuniform. Examples of the pressure die include a coat hanger die, a “T”die, and the like, and any of these maybe favorably employed. In orderto increase the casting speed, two or more pressure dies may be providedon the metal support and dopes divided into two or more may be cast onthe metal support and the dope amount may be divided and layered. Thethickness of the film may be controlled to a desired thickness bycontrolling the dope concentration, the amount of dope pumped, the spaceof the slit in the die opening, the push-out pressure of the die, thespeed of the metal support body and the like.

The drying process performed on the metal support is one in which a web(a dope film which is formed after a dope is cast on a metal support iscalled a web) is heated on a support and solvents are evaporated.Methods for evaporating solvents, include a method in which hot air isblown from the web side and the backside of the support, a method inwhich heating is carried out from the back surface of the support usingheat transfer by liquid, and a method in which heating is carried outfrom the surface as well as the back surface using heat radiation.Further, these methods are preferably combined. If the web is thin,drying is quick. The temperature of the support may be the same alongthe entire support or may be different depending on the position.

The method for performing drying on the metal support which is used inthe present invention, is preferably a method in which casting is doneon the metal support at a temperature of 0-40° C., and more preferablyat a temperature of 5-30° C. The air for drying the web is preferably30-45° C., but is not limited thereto.

The peeling process is one in which a web, in which the organic solventshave been evaporated on the support, is peeled prior to conveying of themetal support. The peeled web is sent to the drying process. Theposition at which the web is peeled from the metal support is called thepeeling point, and the rollers which aid in the peeling are calledpeeling rollers. This phenomenon depends on the thickness of the web,but when the residual solvent amount (represented by the formuladescribed below) is too large, it may be difficult to peel the web. Onthe contrary, when peeling is carried out after fully drying the web onthe support, a part of the web may peel before the peeling position. Itis generally preferable that web peeling is performed when the residualsolvent amount is 20 to 180 percent by weight. The residual solventamount in the present invention when the film is peeled is preferably20-40 percent by weight or 60-150 percent by weight, and 80-140 percentby weight is particularly preferable. One method for increasing thespeed of film production (the film production speed can be increasedbecause the peeling is performed when the residual solvent amount is amuch as possible) is a gel casting method in which peeling can be doneeven when the residual solvent amount is high. The gel casting methodsinclude a method in which poor solvents with respect to the celluloseester are added to a dope and gelling is carried out after casting thedope, and also a method in which gelling is carried out by decreasingthe temperature of a support, and the like. There is further a method inwhich metal salts are added to the dope. By strengthening the web filmthrough gelling the dope on the support, it is possible to carry outearlier peeling and to increase the film formation speed. When thepeeling is carried out at the time when the residual solvent amount isstill great, the web may be too soft, and during peeling, the flatnessof the web is compromised, and formation of wrinkles and longitudinalstreaks due to the peeling tension become likely. Accordingly, theresidual solvent amount is determined such that economic operation andquality are balanced.

The residual solvent amount used in the present invention is expressedby the formula below.Residual solvent amount (percent by weight)={(M−N)/N}×100In the formula, M represents the weight of the web at a suitablyselected point and N represents the weight when M is dried for 3 hoursat 110° C.

Furthermore, it is preferable that in the process for drying thecellulose ester film, the film that has been peeled from the support isfurther dried to cause the residual solvent amount to 2.0 percent byweight or less, and more preferably 1.0 percent by weight or less, andstill more preferably 0.5 percent by weight or less.

In the drying process, the web is dried by employing a method in whichthe web is conveyed through rolls placed in a staggered way and dryingdevice or a tenter drying device in which the web is conveyed whileholding both edges of the web using clips and maintaining web width orslightly stretching the web in the width direction. In the presentinvention, it is particularly favorable to maintain or stretch the webwidth in a suitably selected process subsequent to peeling of the web bythe tenter drying device and at a suitably selected point where theresidual solvent amount is great, since humidity stability of theoptical properties are favorable. The means for drying the web is notparticularly limited and the drying is generally carried out by hot air,infrared rays, heat rolling or microwaves. It is preferable that thedrying is performed by hot air in view of simplicity. The dryingtemperature is preferably gradually increased in the range from 40 to180° C. and more preferably in the range from 50 to 160° C. A longerdrying time at a higher temperature is preferable to decrease Ro and Rt.

The cellulose ester film of the present invention is preferablystretched by 1% both in MD (the film transport direction) and TD (thetransverse direction orthogonal to MD), in order to obtain sufficientflatness of the film. For obtaining a small in-plane retardation values,the stretching ratios in MD and in TD are preferably similar, however,the ratios may be different, provided that the total stretching ratio inthe MD and TD directions is controlled small, in order to have smallerRt. Also, in order to have a smaller Rt, every stretching is preferablycarried out at a higher temperature.

The stretching operation may be performed in a plurality of stages andthe web is preferably stretched biaxially in the casting direction andthe width direction. Furthermore, biaxial stretching may be performedsimultaneously or stepwise. In this case stepwise means that, forexample, stretching in different directions can be performedsequentially, or stretching in the same direction can be performed inmany stages and then the stretching in the different direction is addedat the end of any of those stages.

The width of the cellulose ester film is not less than 1.3 m, andpreferably in the range of 1.4-4 m in view of productivity in that alarge liquid crystal display is obtained. The length of the film woundin a roll is preferably 100-10000 m and more preferably 500-6000 m.

The cellulose ester film of the present invention is suitable to preparea polarizing plate employed in the In-Plane-Switching mode type (alsocalled an IPS mode type) liquid crystal display. Retardation values Roand Rt are preferably in the range of 0 nm≦Ro≦10 nm and −30 nm≦Rt≦20 nm,but are more preferably 0 nm≦Ro≦5 nm and −20 nm≦Rt≦3 nm. By controllingthe retardation values Ro and Rt within 0≦Ro≦5 nm and −20≦Rt≦3 nm,obtained is a cellulose ester film which, further, tends not to besuffered from rupture problem and provides excellent visibility. The Roand Rt values are specifically preferably 0≦Ro≦5 nm and −20≦Rt≦0 nm.Since nx≧ny in Formula (a), Ro never has a negative value.Ro=(nx−ny)×d   Formula (a)Rt={(nx+ny)/2−nz}×d   Formula (b)wherein Ro represents the in-plane retardation value of the film; Rtrepresents the retardation value in the film thickness direction; nxrepresents the in-plane refractive index of the film in the advancedaxis direction; nz represents the refractive index in the film thicknessdirection (each of the refractive indices determined at a wavelength of590 nm); and d represents thickness (nm) of the film.

It is possible to determine retardation values Ro and Rt employing anautomatic double refractometer. For example, determination is performedat 23° C. and 55% relative humidity employing KOBRA-21 ADH (produced byOji Scientific Instruments).

Further, any variation of Ro in the lateral or longitudinal direction offilm is preferably within ±5 nm, is more preferably within ±3 nm, isstill more preferably within ±1 nm, but is most preferably within ±0.3nm.

Further, the variation of Rt in the lateral or longitudinal direction offilm is preferably within ±5 nm, is more preferably within ±3 nm, but ismost preferably within ±1 nm.

The variation of Ro and Rt is preferably within the above range over thetotal length of a long-length film, and also between successive rolls.

The variation of Rt prior to and after heat treatment for 300 hours at80° C. and 90% relative humidity is preferably within ±10 nm, is morepreferably within ±5 nm, but is most preferably within ±1 nm.

(Wavelength Dispersion Characteristic of Ro)

(Wavelength Dispersion Characteristic)

By employing an automatic birefringence analyzer KOBURA-21 ADH (producedby Oji Scientific Instruments), in-plane retardation values atwavelengths of 450, 590, and 650 nm were determined at 23° C. and 55%Relative humidity. Each of the recorded values was designated as R450,R590, and R650, respectively.

Preferred ranges are: 0.7<R450/R590<1.5 and 0.7<R650/R590<1.5, whilemore preferred ranges are: 0.8<R450/R590<1.0, and 1.0<R650/R590<1.3.

(Stability of Rt Against Humidity)

In regard to Rt stability in humility, any variation of Rt between 20%and 80% relative humidity at 23° C. is preferably at most 30 nm, is morepreferably at most 20 nm, but is most preferably at most 10 nm.

(Stability of Rt Against Temperature)

The variation of Rt between 10-60° C. is preferably ±10 nm whileutilizing the value determined at 20° C. and 55% relative humidly as astandard, is more preferably ±5 nm, but is most preferably ±1 nm.

(Stability of Ro Against Temperature)

The variation of Ro between 10-60° C. is preferably ±10 nm whileutilizing the value determined at 20° C. and 55% relative humidly as astandard, is more preferably ±5 nm, but is most preferably ±1 nm.

(Orientation Angle)

When Ro is at most 5 nm, particularly 0-1 nm, the orientation angle isnot particularly limited. However, the orientations angle is commonlywithin ±10 degrees against the lateral or longitudinal direction oflong-lengths of film, is preferably within 5 degrees, is more preferablywithin ±1 degree, but is most preferably within ±0.1 degree.

Orientation angle, as described herein, refers to the delayed phase axisdirection (the angle to the traverse direction during film casting) onthe plane of cellulose ester film. It is possible to determine theorientation angle employing an automatic birefringence analyzerKOBURA-21 ADH (produced by Oji Scientific Instruments).

(Photoelastic Coefficient)

The photoelastic coefficient of the cellulose ester film employed in thepresent invention is preferably 1×10⁻¹⁴−1×10⁻⁹ Pa⁻¹, but is morepreferably 5×10⁻¹²−2×10⁻¹¹. It is possible to determine the photoelasticcoefficient under conditions of 23° C. and 55% relative humidity,employing an ELLIPSOMETER M-150 produced by JASCO Corp. Commercial TACfilms exhibit a photoelastic coefficient of approximately 1×10⁻¹¹ Pa⁻¹.

(Dimensional Stability)

Dimensional variation in the longitudinal and traverse directions oflong lengths of film prior to and after allowing the film to stand at90° C. of no humidity for 100 hours is preferably within ±0.5%, is morepreferably within ±0.3%, but is most preferably ±0.1%. It is preferablethat the film exhibits the same variation as above even after 500 hoursof the above treatment.

Dimensional variation in the longitudinal and lateral directions of along length of film prior to and after allowing the film to stand at 60°C. and relative humidity 90% for 100 hours is preferably within ±1%, ismore preferably within ±1%, is still more preferably within 0.3%, is yetmore preferably within 0.3%, but is most preferably ±0.1%. It ispreferable that the film exhibits the same variation ranges as aboveeven after 500 hours of the above treatment.

The above dimensional variation ratio was determined as follows. Afterre-humidifying a sample film in a room maintained at temperature 23° C.and 55% relative humidity for 4 hours, markings at an interval of about10 cm in the lateral and longitudinal directions were made employing acommon cutter, and the distance (L1) between the markings was measured.Subsequently, the resulting film was allowed to stand in an incubatormaintained at 60° C. and 90% relative humidity for 24 hours. Afterrehumidifying the film in the room maintained at 23° C. and 55% relativehumidity, the distance (L2) between the markings was recorded. Thedimensional variation ratio was evaluated based on the followingformula.Dimensional variation ratio (%)={(L2−L1)/L1}×100

The dimensional variation ratio was also determined in the same manneras above, except that the storage conditions of 60° C. and 90% relativehumidity for 24 hours were changed to those of 90° C. and no humidityfor 24 hours.

(Water-Vapor Permeability)

Water-vapor permeability at 40° C. and 90% relative humidity ispreferably 1-1,500 g/m²·24 hours, is more preferably 5-1,200 g/m²·24hour, and is still more preferably 10-1,000 g/m²·24 hours.

(Light Transmittance)

The transmittance at 500 nm of the cellulose ester film of the presentinvention is preferably 85-100%, is more preferably 90-100%, but is mostpreferably 92-100%. Further, transmittance at 400 nm is preferably40-100%, is more preferably 50-100%, but is most preferably 60-100%.(Determination of Light Transmittance) Transmittance T was determined asfollows. Spectral transmittance τ(λ) in the wavelength range of 350-700nm of each sample was recorded at an interval of 10 nm, employing aspectrophotometer U-3400 (produced by Hitachi, Ltd.), whereby thetransmittance values at specific wavelengths were obtained.

(Absorbability of Ultraviolet Radiation)

Light transmittance at 380 nm of a cellulose ester film incorporating noUV absorbers is preferably at least 50%, is more preferably at least80%, but is most preferably at least 90%. When UV absorbers areincorporated, transmittance at 380 nm is preferably less than 50%, ismore preferably 0-15%, is still more preferably 0-10%, but is mostpreferably less than 5%. It is possible to readily control theabsorbability of ultraviolet radiation by varying the type and additionamount of additives such as UV absorbers, plasticizers, resins, orminute particles.

In the same manner as above, it is also possible to determine theabsorbability of ultraviolet radiation, employing a spectrophotometer,U-3400 (produced by Hitachi. Ltd.).

(Haze)

The haze of the cellulose ester film of the present invention, whendetermined by stacking up three sheets, is preferably at most 5%, ismore preferably at most 2%, but is most preferably at most 1%. It ispossible to determine the haze value based on JIS K 6714, employing ahaze meter (1001 Type DP, produced by Nippon Denshoku Industries Co.,Ltd.).

(Elastic Modulus)

The elastic modulus of the cellulose ester film of the present inventionis preferably 1-6 GPa, but is more preferably 2-5 GPa.

Elastic moduli in the traverse direction (TD) and manufacturingdirection (MD) of long-lengths of film may be the same or different. Itis preferable that 0.5≦MD elastic modulus/TD elastic modulus≦2; it ismore preferable that 0.7≦MD elastic modulus/TD elastic modulus≦1.4; butis still more preferable that 0.9≦MD elastic modulus/TD elasticmodulus≦1.1.

(Elongation at Break)

The elongation at break of the cellulose ester film of the presentinvention is preferably in the range of 10-90% at 23° C. and 55%relative humility, but is more preferably in the range of 20-80%.Further, the break stress is preferably in the range of 50-200 Mpa.(Elastic Modulus, Elongation at Break, and Break Stress of Films)Measurement was carried out at 23° C. and 55% relative humidityaccording to the method described in JIS K 7127. The above values weredetermined as follows. A sample sheet was cut into 10 mm wide and 130 mmlong strips. Subsequently, tests were carried out in such a manner thatat an appropriate temperature, the distance between chucks was set at100 mm and pulling was carried out at a rate of 100 mm/minute.

(Tear Strength)

The tear strength of the cellulose ester film of the present inventionis preferably 1-50 g, is more preferably 3-30 g, but is most preferably5-25 g. It is possible to determine the tear strength as follows. Afterrehumidifying a film sheet at 23° C. and 55% relative humidity for 24hours, the resulting sheet is cut into strips of 50 mm wide×64 mm, andit is possible to measure the tear strength of the strip based on ISO6383/2-1983.

The range is preferably 0.5<Htd/Hmd<2, but is more preferably0.7<Htd/Hmd<1.3, wherein Htd represents the tear strength in thetraverse direction (TD direction) and Hmd represents the tear strengthin the manufacturing direction (MD direction). When cellulose ester filmis stretched in the traverse direction, it is possible to control theratio of tear strength of the film in the manufacturing direction(hereinafter referred to as the MD direction) employing the stretchingdirection, the stretching factor, and the stretching temperature.

(Contact Angle)

When the cellulose ester film of the present invention is employed as apolarizing plate protective film, in order to enhance adhesionproperties to the polarizer, an alkali saponification treatment isoccasionally carried out. It is preferable that a film which has beensubjected to the alkali treatment is adhered onto a polarizer employingan aqueous polyvinyl alcohol solution as an adhesive. The contact angleof pure water on the surface of the film prior to saponification ispreferably 40-80 degrees, but is more preferably 50-70 degrees. Thecontact angle after saponification treatment becomes preferably at most30 degrees, but becomes more preferably 5-25 degrees. The contact angleon both surfaces of the film may be the same or slightly different. Forexample, it is possible that the content of additives in the surfacewhich is brought into contact with a casting support (being a metal drumor belt) of additives is varied from the opposite side, whereby it ispossible to differ the contact angle on both sides. It is possible todetermine the surface which is to face the polarizer, based on the yieldof the polarizing plate production, curling of the finished polarizingplates, and coatability of functional layers provided onto the celluloseester film.

(Contact Angle After Saponification)

A sample was treated with 2.5 N NaOH at 50° C. for 2.5 minutes, andsubsequently washed with pure water for 2.5 minutes. After the abovetreatment, the sample was rehumidified at 23° C. and 55% relativehumidity for 24 hours, and the contact angle was determined employing acontact angle meter, Type CA-D, produced by Kyowa Interface Science Co.,Ltd.

(Dissolution Into a Saponification Solution)

When a large amount of additives in the film and their decompositionproducts by an alkali saponification is eluted, the saponificationsolution is stained and problems result due to foreign matter.Consequently, it is preferable to keep the elution as little aspossible. Generally, it is possible to decrease the elution amount byreducing low molecular weight components or employing additives whichexhibit excellent compatibility with cellulose ester. Additives, whichhardly result in bleeding-out during high temperature processing or hightemperate and high humidity processing, are preferred since they hardlyelute into the saponification solution.

(Curling)

Curling of cellulose ester films in the longitudinal or traversedirection is preferably in the range of −20 to 20 l/m, is morepreferably in the range of −15 to 15 l/m, but is most preferably in therange of −10 to 10 l/m.

The above curling is determined as follows. After allowing a film sheetto stand at 25° C. and 55% relative humidity for 24 hours, the resultingfilm sheet is cut into strips of 50 mm×2 mm. The strips are rehumidifiedat 23° C. and 55% relative humidity for 24 hours, and then the curlingvalue of each of film strips is determined employing a radius ofcurvature. The numerical curl value is determined based on Method “A” ofJIS K 7619.

The curling value is expressed by 1/R, where R represents the radius ofcurvature and meter is employed as the unit.

It is possible to determine adhesion of a polarizer to any of the sidesof a cellulose ester film based on curling of the polarizing protectivefilm employed on the opposite side and the entire polarizing plateincluding, if any, a hard coat layer, an antiglare layer, anantireflection layer, an optical anisotropic layer, a light scatteringlayer or a brightness enhancing film, and productivity of the polarizingplates.

(Water Absorption Ratio)

When a cellulose ester film is employed as a polarizing plate protectivefilm, its water absorption ratio is preferably 1-5%. When the waterabsorption ratio is at least 1%, a polarizer adhered onto a protectivefilm is readily dried during preparation of a polarizing plate, whilewhen it is less than 5%, the resulting polarizing plate exhibitsexcellent durability.

(Measurement Method of the Water Absorption Ratio) A sample is cut to 10cm×10 cm, and immersed into 23° C. water for 24 hours. After removalfrom the water, water droplets on both sides are immediately wiped offby using a filter paper and the weight is recorded and designated as W1.Subsequently, after rehumidifying the above film at 23° C. and 55%relative humidity for 24 hours, the resulting weight is recorded anddesignated as W0. Thus, the water absorption ratio during the immersionin water for 24 hours is calculated based on the following formula,employing each of the recorded values.Water absorption ratio (%)={(W1−W0)/W}×100(Moisture Regain)

When a cellulose ester film is employed as a polarizing plate protectivefilm, its moisture regain is preferably 1-4.5%. The moisture regain ofat least 1% results in desired drying properties when a polarizer isadhered to a protective film and dried during preparation of apolarizing plate, while the moisture regain of less than 4.5% results inexcellent durability of the polarizing plate.

(Measurement Method of Moisture Regain)

A sample is cut to 10 cm×10 cm, and rehumidified at 23° C. and 80%relative humidity for 48 hours. Thereafter, the weight is recorded anddesignated as W3. Subsequently, after drying the above film at 120° C.for 45 minutes, the resulting weight is recorded and designated as W2.Thus, the moisture regain is calculated based on the following formula,employing each of the recorded values.Moisture regain (%)={(W3−W2)/W2}×100(Layer Thickness)

It is preferable that the cellulose ester film is thin, because theresulting polarizing plate is also thin, and this contributes to easilyproduce a thin liquid crystal display. However if the film is too thin,transparency and tear strength deteriorate. The thickness of thecellulose ester film that achieves a balance between the two ispreferably 10-100 μm, more preferably 10-80 μm and specificallypreferably 10-70 μm. The variations in the thickness in the lateraldirection and in the longitudinal direction are preferably ±5 μm, morepreferably ±3 μm, still more preferably ±1 μm, further more preferably±0.5 μm and specifically preferably ±0.1 μm, in an average thickness.

Layer thickness variation refers to the difference between the maximumvalue and the average value, or between the minimum value and theaverage value, wherein the average value is determined in such a mannerthat after rehumidifying a sample film at 23° C. and 55% RH for 24hours, the thickness is determined at intervals of 10 mm, and thenaveraged. (Surface Roughness (Ra) of Film)

(Center Line Mean Roughness (Ra) of Cellulose Ester Film)

When a cellulose ester film is employed as an LCD member, to minimizelight leakage, a high degree of flatness is required. The center linemean roughness (Ra) is the value specified in JIS B 0601. Examples ofthe measurement methods include a needle contact method and an opticalmethod.

Center line mean roughness (Ra) of the cellulose ester film of thepresent invention is preferably at most 20 nm, is more preferably atmost 10 nm, but is most preferably at most 3 nm. It is possible todetermine the center line mean roughness Ra employing a non-contactsurface fine structure meter WYKO NT-2000.

(Image Clarity)

It is preferable that the image clarity of cellulose ester films ishigh. The above image clarity is defined in JIS K 7105. When determinedemploying a 1 mm slit, at least 90% is preferred, at least 95% is morepreferred, but at least 99% is most preferred.

It is preferable that the cellulose ester film of the present inventionresults in minimal foreign matter bright spots. Foreign matter brightspots, as described herein, refer to the following type of spots. Acellulose ester film is placed between two polarizing plates arranged atright angles (crossed Nicols) and light is exposed on one side while isviewed from the other side. The foreign matter bright spots are thosewhich are seen due to leakage of light from the light source. Duringthis operation, a polarizing plate, which is employed for evaluation, iscomposed of a protective film which results in no foreign matter brightspots, whereby a glass plate is preferably employed to protect thepolarizers. It is assumed that one of the causes of foreign matterbright spots is the presence of cellulose, incorporated in celluloseester, which has undergone no acetylation. It is possible to reduceforeign matter bright spots by employing cellulose ester incorporatingminimal foreign matter and filtering the cellulose ester solution.Further, as the film thickness decreases, the number of foreign matterbright spots per unit area tends to decrease. As the content ofcellulose ester incorporated in films decreases, foreign matter brightspots also tends to decrease.

The number of foreign matter bright spots at a diameter of at least 0.01mm is preferably at most 200/cm², is more preferably at most 100/cm², isstill more preferably at most 50/cm², is yet more preferably at most10/cm², but is most preferably 0/cm². Further, the number of foreignmatter bright spots at a dimer of 0.005-0.01 mm is preferably at most200/cm², is more preferably at most 100/cm², is still more preferably50/cm², is yet more preferably 30/cm², is further more preferably atmost 10/cm², but is most preferably 0/cm².

(Determination of Foreign Matter Bright Spots)

A sample was interposed between two polarizers arranged at right angles(crossed Nicols) and light was exposed onto the exterior side of apolarizing plate. Subsequently, the other side of the polarizing platewas observed via a microscope (at a factor of 30 in terms oftransmission light source) and the number of visible white spots per 25mm² was recorded. Determination was conducted for 10 areas and thenumber of foreign matter bright spots for a total area of 250 mm² wasrecorded, and then the number of foreign matter bright spots/cm² wascalculated and employed for evaluation.

(Distribution of Additives in the Thickness Direction)

Additives such as plasticizers, resins, or UV absorbers may beincorporated uniformly or non-uniformly through the thickness directionof the film. For example, it is possible to decrease the content ofplasticizers in the surface to 50-99.9% with respect to the averagecontent of the plasticizers through the overall thickness, and it isalso possible to increase the content of the plasticizes to 100.1-150%in the surface. An example case is that the concentration of additivesnear the surface is decreased by scattering them near the surface due toan increase in drying temperature. An example is that a cast film ispeeled under drying condition to result in non-uniform content ofresidual solvents or non-uniform solvent compositions and subsequentlythe film is dried whereby the concentration distribution results due tomigration and diffusion of additives through the thickness. The degreeof distribution varies depending on additives. Further, it is possibleto provide a layer incorporating additives in differing amounts on thesurface via successive casting or co-casting. When additivesintentionally or unintentionally results in a content distributionthrough the thickness, it is possible to determine the side onto which afunctional layer is applied or to which a polarizer is adhered, uponconsidering the productivity of each of the converting processes andpost processes.

It is preferable that the cellulose ester film of the present inventionis employed as a liquid crystal display member due to its highwater-vapor permeability and dimensional stability. The liquid crystaldisplay member, as described herein, refers to a member employed inliquid crystal display units. Examples include a polarizing plate, apolarizing plate protective film, a retardation plate, a reflectionplate, a viewing angle enhancing film, an optical compensation film, anantiglare film, a non-reflection film, an antistatic film, anantireflection film, a light diffusion film and a brightness enhancingfilm. Of these, it is preferable to employ a cellulose ester film as thepolarizing plate, as the polarizing plate protective film, and as theantireflection film. Specifically, when employed in the uppermostsurface of a liquid crystal display as a polarizing plate protectivefilm, it is preferable to provide the antireflection layer on the filmsurface.

(Antireflection Layer)

The antireflection layer based on light diffraction, employed in thepresent invention, will now be described.

(Antireflection Layer Configuration)

It is possible to constitute the antireflection layer, employed in thepresent invention, employing a single layer configuration composed ofonly a low refractive index layer or a multi-refractive index layer.Layers are applied onto a hard coat layer (being a clear hard coat layeror an antiglare layer) on a transparent film substrate to decreasereflectance due to optical diffraction, while considering the refractiveindex, the layer thickness, the number of layers, and the order oflayers. The antireflection layer may be composed of the combination of ahigh refractive index layer which exhibits a higher refractive indexthan the support and a low refractive index layer which exhibits a lowerrefractive index than the support. An antireflection layer composed ofat least three refractive index layers is particularly preferred, inwhich three layers, which differ in refractive index, are coated in theorder from the support of a medium refractive index layer (exhibiting ahigher refractive index than the support or the hard coat layer and alower refractive index than the high refractive index layer)/a highrefractive index layer/a low refractive index layer. The hard coat layermay function as a high refractive index layer.

Examples of preferred layer configuration of the antireflection film ofthe present invention will now be described. Herein, “/” represents thearrangement of a layer upon a layer.

Back coat layer/support/hard coat layer/low refractive index layer

Back coat layer/support/hard coat layer/high refractive index layer/lowrefractive index layer

Back coat layer/support/hard coat layer/medium refractive indexlayer/high refractive index layer/low refractive index layer

Back coat layer/support/antistatic layer/hard coat layer/mediumrefractive index layer/high refractive index layer/low refractive indexlayer

Antistatic layer/support/hard coat layer/medium refractive indexlayer/high refractive index layer/low refractive index layer

Back coat layer/support/hard coat layer/high refractive index layer/lowrefractive index layer/high refractive index layer/low refractive indexlayer

It is possible to further provide a stain resistance layer on theuppermost low refractive index layer. Fluorine-incorporating organiccompounds are preferably employed in the stain resistance layer.

(Actinic Ray Curable Resin Layer)

In the present invention, a hard coat layer is preferably provided onthe above-described cellulose ester film. The production method of anactinic ray curable resin layer employed as a hard coat layer will nowbe described.

An actinic ray curable resin layer is preferably employed as a hard coatlayer to be used for the cellulose ester film of the present invention.

The actinic ray curable resin layer refers to a layer which contains, asa main component, a resin cured through a crosslinking reaction whenexposed to actinic rays such as UV light or electron beams. The actinicray curable resin layer preferably contains an ethylenically unsaturatedmonomer, which is exposed to actinic rays such as UV light or electronbeams and cured to form a hard coat layer. Listed as representativeactinic ray curable resins are UV curable resins as well as electronbeam curable resins. The actinic ray curable resin is preferably a UVcurable resin.

Listed as UV curable resins may be, for example, UV curable urethaneacrylate resins, UV curable polyester acrylate resins, UV curable epoxyacrylate resins, UV curable polyol acrylate resins, or UV curable epoxyresins.

The UV curable urethane acrylate resins are easily prepared in such amanner that acrylate based monomers having a hydroxyl group such as2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate (hereinafter,acrylate includes acrylate itself and methacrylate, and acrylaterepresents both), or 2-hydroxypropyl acrylate are allowed to react withthe product which is commonly prepared by allowing polyester polyols toreact with isocyanate monomers or prepolymers. For example, thosedescribed in Japanese Patent O.P.I. Publication No. 59-151110 can beused.

For example, preferably employed is a mixture comprising 100 parts ofUnidick 17-806 (manufactured by Dainippon Ink and Chemicals Inc.) andone part of Coronate L (manufactured by Nippon Urethane Industry Co.,Ltd.).

The UV ray curable polyesteracrylate resins include those preparedeasily by reacting a polyesterpolyol with 2-hydroxyethylacrylate or2-hydroxypropylacrylate, disclosed for example, in JP-A No. 59-151112.

Examples of the UV ray curable epoxyacrylate resin include thoseprepared by reacting an epoxyacrylate oligomer in the presence of areactive diluting agent and a photoinitiator, disclosed for example, inJP-A No. 1-105738.

Examples of the UV ray curable polyol acrylate resin includetrimethylolpropane triacrylate, ditrimethylolpropane tetraacrylate,pentaerythritol triacrylate, pentaerythritol tetraacrylate,dipentaerythritol hexaacrylate or alkyl-modified dipentaerythritolpentaacrylate.

The photoinitiators for the UV ray curable resins include benzoine orits derivative, or acetophenones, benzophenones, hydroxy benzophenones,Michler's ketone, α-amyloxime esters, thioxanthones or their derivativesan oxime ketone derivative, a benzophenone derivative or a thioxanthonederivative. These photoinitiators may be used together with aphoto-sensitizer. The above photoinitiators also work as aphoto-sensitizer. Sensitizers such as n-butylamine, triethylamine andtri-n-butylphosphine can be used in photo-reaction of epoxyacrylates.The content of the photoinitiators or sensitizers in the UV ray curableresin layer is 0.1 to 15 parts by weight, and preferably 1 to 10 partsby weight, based on the 100 parts by weight of the UV ray curable resinlayer.

The polymerizable monomers having one unsaturated double bond in themolecule include methyl acrylate, ethyl acrylate, butyl acrylate, benzylacrylate, cyclohexyl acrylate, vinyl acetate, and styrene. Thepolymerizable monomers having two or more unsaturated double bonds inthe molecule include ethylene glycol diacrylate, propylene glycoldiacrylate, divinylbenzene, 1,4-cyclohexane diacrylate,1,4-cyclohexyldimethyl diacrylate, trimethylol propane triacrylate, andpentaerythritol tetraacrylate.

The UV curable resins available on the market utilized in the presentinvention include Adekaoptomer KR, BY Series such as KR-400, KR-410,KR-550, KR-566, KR-567 and BY-320B (manufactured by Asahi Denka Co.,Ltd.); Koeihard A-101-KK, A-101-WS, C-302, C-401-N, C-501, M-101, M-102,T-102, D-102, NS-101, FT-102Q8, MAG-1-P20, AG-106 and M-101-C(manufactured by Koei Kagaku Co., Ltd.); Seikabeam PHC2210(S), PHCX-9(K-3), PHC2213, DP-10, DP-20, DP =30, P1000, P1100, P1200, P1300,P1400, P1500, P1600, SCR900 (manufactured by Dainichiseika Kogyo Co.,Ltd.); KRM7033, KRM7039, KRM7131, UVECRYL29201 and UVECRYL29202(manufactured by Daicel U. C. B. Co., Ltd.); RC-50i5, RC-5016, RC-5020,RC-5031, RC-5100, RC-5102, RC-5120, RC-5122, RC-5152, RC-5171, RC-5180and RC-5181 (manufactured by Dainippon Ink & Chemicals, Inc.); OlexNo.340 Clear (manufactured by Chyugoku Toryo Co., Ltd.); Sunrad H-601,RC-750, RC-700, RC-600, RC-500, RC-611 and RC-612 (manufactured by SanyoKaseikogyo Co., Ltd.); SP-1509 and SP-1507 (manufactured by SyowaKobunshi Co., Ltd.); RCC-15C (manufactured by Grace Japan Co., Ltd.) andAronix M-6100, M-8030 and M-8060 (manufactured by Toagosei Co., Ltd.).

Concrete examples include trimethylol propane triacrylate, ditrimethylolpropane tetracrylate, pentaerythritol triacrylate, pentaerythritoltetracrylate, dipentaerythritol hexaacrylate and alkyl modifieddipentaerythritol pentaacrylate.

These actinic ray curable resin layers can be applied by any method wellknown in the art, for example: a gravure coater, a dip coater, a reversecoater, a wire bar coater, a die coater and ink jet printing.

Light sources to cure layers of UV curable-resin by photo-curingreaction are not specifically limited, and any light source may be usedas far as UV ray is generated. For example, a low-pressure mercury lamp,a medium-pressure mercury lamp, a high-pressure mercury lamp, anultrahigh-pressure mercury lamp, a carbon arc lamp, a metal halide lampand a xenon lamp may be utilized. The preferable irradiation quantity oflight may be changed depending on the type of lamp, however, it ispreferably from 5 to 150 mJ/cm², and more preferably from 20 to 100mJ/cm².

Irradiation of an actinic ray is preferably carried out under tension inthe longitudinal direction of the film and more preferably under tensionin both the lateral and the longitudinal directions. The preferabletension is from 30 to 300 N/m. The method to apply tension to the filmis not specifically limited and tension may be applied while the film istransported with back rolls or may be applied in a tenter in the lateraldirection or in the biaxial directions of the film, whereby a celluloseester film exhibiting a superior flatness can be obtained.

An organic solvent used for a coating solution of the UV curable-resincan be selected from, for example, hydrocarbons (toluene and xylene),alcohols (methanol, ethanol, isopropanol, butanol and cyclohexanol),ketones (acetone, methylethyl ketone and methylisobutyl ketone), esters(methyl acetate, ethyl acetate and methyl lactate), glycol ethers andother organic solvents. These organic solvents may be also used incombination. The above mentioned organic solvents preferably containpropylene glycol monoalkyl ether (the alkyl having 1 to 4 carbon atoms)or propylene glycol monoalkyl ether acetate (the alkyl having 1 to 4carbon atoms) in an amount of 5% by weight or more, and more preferablyfrom 5 to 80% by weight.

In a coating solution of a UV ray-curable resin, a silicon compound suchas a polyether modified silicone oil, is preferably added. The numberaverage molecular weight of the polyether modified silicone oil ispreferably from 1,000 to 100,000 and more preferably from 2,000 to50,000. Addition of the polyether modified silicone oil with a numberaverage molecular weight of less than 1,000 may lower the drying rate ofthe coating solution, while that of more than 100,000 may be difficultto bleed out at the surface of the coated film.

Silicon compounds available on the market include, for example: DKQ8-779(a trade name of Dow Corning Corp.), SF3771, SF8410, SF8411, SF8419,SF8421, SF8428, SH200, SH510, SH1107, SH3771, BX16-034, SH3746, SH3749,SH8400, SH3771M, SH3772M, SH3773M, SH3775M, BY-16-837, BY-16-839,BY-16-869, BY-16-870, BY-16-004,BY-16-891, BY-16-872, BY-16-874,BY22-008M, BY22-012M, FS-1265 (all being trade names of Dow CorningToray Silicone Co., Ltd.), KF-101, KF-100T, KF351, KF352, KF353, KF354,KF355, KF615, KF618, KF954, KF6004, siliconeX-22-945, X22-160AS (allbeing trade names of Shin-Etsu Chemical Co., Ltd.), XF3940, XF3949 (bothbeing trade names of Toshiba Silicones Co., Ltd.), DISPARLONLS-009 (atrade name of Kusumoto Chemicals Ltd.), GLANOL410 (a trade name ofKyoeisha Chemicals Co., Ltd.), TSF4440, TSF4441, TSF4445, TSF4446,TSF4452, TSF4460 (all being trade names of GE Toshiba Silicones Co.,Ltd.), BYK-306, BYK-330, BYK-307, BYK-341, BYK-361 (all being tradenames of BYK-Chemie Japan KK) L Series (L-7001, L-7006, L-7604 andL-9000), Y Series and FZ Series (FZ-2203, FZ-2206 and FZ-2207) (all fromNippon Unicar Co., Ltd.).

These compositions may improve the coating ability of a coating solutiononto a substrate or an under coat layer. These compounds used in the toplayer of film may contribute to improve scratch resistance of the filmas well as water-resistance, oil-resistance and anti-stain properties ofthe film. The content of the silicon compound is preferably from 0.01 to3% by weight based on the solid components in the coating solution.

The aforementioned coating methods are also used as coating method of aUV ray-curable resin layer coating solution. The wet thickness of thecoated UV-curable resin layer is preferably from 0.1 to 30 μm and morepreferably from 0.5 to 15 μm. The dry thickness of the coated UV-curableresin layer is preferably from 0.1 to 20 μm and more preferably from 1to 10 μm.

The UV ray-curable resin layer is preferably irradiated with UV raysduring or after drying. The duration of UV ray irradiation is preferablyfrom 0.1 seconds to 5 minutes in order to secure the exposure amountfrom 5 to 150 mJ/cm² as mentioned above. In view of working efficiencyand hardening efficiency of the UV-curable resin layer, the duration ismore preferably from 0.1 to 10 seconds.

Intensity of the actinic ray is preferably from 50 to 150 mW/m² on theirradiated surface.

The UV-cured resin layer thus obtained may preferably contain inorganicor organic microparticles in order to attain the characteristics of ananti-blocking property, scratch resistance, an antiglare property or alight diffusing property.

Examples of inorganic microparticles used in the hard coat layer includesilicon oxide, titanium oxide, aluminum oxide, zirconium oxide,magnesium oxide, calcium carbonate, talc, clay, calcined kaolin,calcined calcium silicate, hydrated calcium silicate, aluminum silicate,magnesium silicate and calcium phosphate. Among these, silicon oxide,titanium oxide, aluminum oxide, zirconium oxide, magnesium oxide arespecifically preferable.

Examples of organic microparticles include: particles of polymethacrylicacid methyl acrylate resin, acryl-styrene based resin, polymethylmethacrylate resin, silicon based resin, polystyrene based resin,polycarbonate resin, benzoguanamine based resin, melamine based resin,polyolefin based resin, polyester based resin, polyamide based resin,polyimide based resin and polyfluorinated ethylene based resin.Specifically preferable organic microparticles include, for example:microparticles of cross-linked polystylene (such as SX-130H, SX-200H andSX-350H manufactured by Soken Chemical & Engineering Co., Ltd.) andpolymethyl methacrylate (such as MX150 and MX300 manufactured by SokenChemical & Engineering Co., Ltd.).

The average particle diameter of the microparticles is preferably from0.005 to 5 μm and specifically preferably from 0.01 to 1 μm. Themicroparticle content of the hard coat layer is preferably from 0.1 to30 weight parts per 100 weight parts of the UV-curable resincomposition.

It is preferred that the UV curable resin layer is a clear hard coatlayer having a center-line average roughness (Ra prescribed by JIS B0601) of 1 to 50 nm or an anti-glare layer Having an Ra value of from0.1 to 1 μm. The center-line average roughness (Ra) is preferablymeasured by means of a surface roughness meter using interference oflight, for example, RST/PLUS manufactured by WYKO Co., Ltd.

(Back Coat Layer)

A back coat layer is preferably provided on the surface reverse to thehard coat layer side surface of the hard coat film of the presentinvention. A back coat film is provided on a cellulose ester film toprevent curling which may occur when a hard coat layer or other layersis formed on a cellulose ester film by means of a coating method or byCVD. Namely, by adding a counter force to curl toward the back coatside, the force to curl may be balanced out. Also, a back coat layerpreferably has a feature to prevent blocking. For this purpose,particles are preferably added to a coating composition of back coatlayer.

Examples of particles preferably added to the back coat layer includeinorganic particles, for example, silicon dioxide, titanium dioxide,aluminum oxide, zirconium oxide, calcium carbonate, talc, clay, calcinedkaolin, calcined calcium silicate, tin oxide, indium oxide, zinc oxide,ITO, hydrated calcium silicate, aluminum silicate, magnesium silicateand calcium phosphate. Particles containing silicon are preferably usedto minimize the haze. Of these, silicon dioxide is specificallypreferable.

These microparticles are available on the marketed with the productnames of, for example, Aerosil R972, R972V, R974, R812, 200, 200V, 300,R202, OX50 and TT600 (produced by Nippon Aerosil Co., Ltd.), and can beused. Microparticles of zirconium oxide are also available on the marketwith the product names of Aerosil R976 and R811 (produced by NipponAerosil Co., Ltd.). Examples of polymer microparticles include: asilicone resin, a fluorine-containing resin and an acryl resin. Ofthese, preferable is a silicone resin, specifically, a silicone resinhaving 3-dimensional net work structure. Examples of a silicone resininclude: TOSPERL 103, 105, 108, 120, 145, 3120 and 240, which aremanufactured by Toshiba Silicone Co., Ltd.

Of these, Aerosil 200V and Aerosil R972V are specifically preferable,since a higher antiblocking property is obtained while keeping a lowhaze. The dynamic friction coefficient of the surface reverse to thehard coat layer side of the hard coat film of the present invention ispreferably not more than 0.9 and more preferably in the range of 0.1-0.9by using these antiblocking agents.

The content of microparticles contained in the back coat layer ispreferably 0.1-50% by weight and more preferably 0.1-10% by weight basedon the weight of the binder. The increase in haze after providing a backcoat layer is preferably not more than 1%, more preferably not more than0.5% and specifically preferably in the range of 0.0-0.1%.

The back coat layer is formed by coating a composition containing asolvent which dissolves or swells the cellulose ester film. As thesolvent, in addition to the mixture of a solvent which dissolves thecellulose ester and a solvent which swells the cellulose ester, asolvent which does not dissolve the cellulose ester may also be added.The mixing ratio of these solvents and the amount of applied coatingcomposition are determined depending on the kind of the resin or degreeof the curl of the film.

A larger curl-preventing effect can be obtained by increasing the amountof a solvent which dissolves or swells the cellulose ester whiledecreasing the amount of a solvent which does not dissolve the celluloseester. The mixing ratio is preferably as follows: (a solvent whichdissolves or swells the cellulose ester):(a solvent which does notdissolve the cellulose ester)=10:0-1:9. Examples of a solvent whichdissolves or swells a transparent resin film include: dioxane, acetone,methylethyl ketone, N,N-dimethylformamide, methyl acetate, ethylacetate,trichloroethylene, methylene chloride, ethylene chloride,tetrachloroethane, trichloroethane and chloroform. Examples of a solventwhich does not dissolve a transparent resin film include: methanol,ethanol, n-propyl alcohol, i-propyl alcohol, n-butanol and hydrocarbons(such as toluene, xylene and cyclohexanol).

These coating compositions are applied on a transparent resin filmpreferably in a wet thickness of 1-100 μm or specifically preferably5-30 μm by using, for example, a gravure coater, a dip coater, a reversecoater, a wire bar coater or a die coater. Examples of a binder resin ofthe back coat layer include: vinyl polymers and copolymers, such as,vinyl chloride-vinyl acetate copolymer, a polyvinyl chloride resin, avinyl acetate resin, vinyl acetate-vinyl alcohol copolymer, partiallyhydrolyzed vinyl chloride-vinyl acetate copolymer, vinylchloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrilecopolymer, ethylene-vinyl alcohol copolymer, chlorinated polyvinylchloride, ethylene-vinyl chloride copolymer and ethylene-vinyl acetatecopolymer; cellulose derivatives, such as, nitrocellulose, celluloseacetate propionate (preferably the acetylation degrees of 1.8-2.3, thepropionyl substitution degree of 0.1-1.0), diacetyl cellulose andcellulose-acetate-butylate; rubber resins, such as, maleic acid-acrylicacid copolymer, acrylic ester copolymer, acrylonitrile-styrenecopolymer, chlorinated polyethylene, acrylonirile-chlorinatedpolyethylene-styrene copolymer, methylmethacrylate-butadiene-styrenecopolymer, an acryl resin, a polyvinyl acetal resin, a polyvinyl butyralresin, a polyester polyurethane resin, a polyether polyurethane resin, apolycarbonate polyurethane resin, a polyester resin, a polyether resin,a polyamide resin, an amino resin, a styrene-butadiene resin, and abutadiene-acrylonirile resin; silicone resins; and fluorine resins.However, the present invention is not limited thereto. Varieties ofhomopolymers and copolymers originated from acryl or metacryl monomersare available on the market and a preferable material can be selectedfrom these, for example: Acrypet MD, VH, MF and V (produced byMitsubishi Rayon Co., Ltd.), Hi Pearl M-4003, M-4005, M-4006, M-4202,M-5000, M-5001 and M-4501 (produced by Negami Chemical Industrial Co.,Ltd.), Dianal BR-50, BR-52, BR-53, BR-60, BR-64, BR-73, BR-75, BR-77,BR-79, BR-80, BR-82, BR-83, BR-85, BR-87, BR-88, BR-90, BR-93, BR-95,BR-100, BR-101, BR-102, BR-105, BR-106, BR-107, BR-108, BR-112, BR-113,BR-115, BR-116, BR-117 and BR-118 (produced by Mitsubishi Rayon Co.,Ltd.)

Specifically preferable are cellulose resins, for example, diacetylcellulose and cellulose acetate propionate.

The back coat layer may be applied before or after providing a layer onthe opposite side to the back coat layer (for example, a clear hard coatlayer or other layer such as an antistatic layer), however, when theback coat layer also has a function of a blocking layer, the back coatlayer is preferably applied earlier. Alternatively, the back coat layermay be applied twice before and after providing the hard coat layer.

<Low Refractive Index Layer>

In the low refractive index layer employed in the the present invention,hollow silica particles are preferably used.

(Hollow Silica Particles)

Hollow silica particles are (I) complex particles constituted of aporous particle and a cover layer arranged on the surface of said porousparticle or (II) hollow particles, the interior of which is hollow andthe hollow is filled with contents such as a solvent, a gas or a poroussubstance. Herein, at least either (I) complex particles or (II) hollowparticles is contained in a low refractive index layer, or the both ofthem may be contained.

Herein, hollow particles are particles the interior of which is hollow,and the hollow is surrounded by a particle wall. The interior of thehollow is filled with the contents such as a solvent, a gas or a poroussubstance which have been utilized in preparation. The mean particlediameter of such hollow particles is preferably in a range of 5-300 nmand preferably of 10-200 nm. The mean particle diameter of hollowparticles utilized is appropriately selected depending on the thicknessof the formed transparent cover film and is preferably in a range of2/3-1/10 of the layer thickness of the transparent cover film of such asa formed low refractive index layer. These hollow particles arepreferably utilized in a state of being dispersed in a suitable mediumto form a low refractive index layer. As dispersing medium, water,alcohol (such as methanol, ethanol and isopropanol), ketone (such asmethyl ethyl ketone and methyl isobutyl ketone) and ketone alcohol (suchas diacetone alcohol) are preferable.

A thickness of the cover layer of a complex particle or the thickness ofthe particle wall of a hollow particle is preferably in a range of 1-20nm and more preferably in a range of 2-15 nm. In the case of a complexparticle, when a thickness of the cover layer is less than 1 nm, aparticle may not be completely covered to allow such as silicate monomeror oligomer having a low polymerization degree as a coating componentdescribed later to immerse into the interior of the complex particleresulting in decrease of porosity of the interior, whereby an effect ofa low refractive index may not be obtained. Further, when a thickness ofthe cover layer is over 20 nm, the aforesaid silicate monomer oroligomer never immerses into the interior, however, the porosity (amicro-pour volume) of a complex particle may be decreased, resulting inan insufficient effect of a low refractive index. Further, in the caseof a hollow particle, particle shape may not be kept when a thickness ofthe particle wall is less than 1 nm, while an effect of a low refractiveindex may not be obtained when a thickness of the particle wall is notless than 20 nm.

The cover layer of a complex particle or the particle wall of a hollowparticle is preferably comprised of silica as a primary component.Further, components other than silica may be incorporated and specificexamples include such as Al₂O₃, B₂O₃, TiO₂, ZrO₂, SnO₂, CeO₂, P₂O₃,Sb₂O₃, MoO₃, ZnO₂, and WO₃. A porous particle to constitute a complexparticle includes those comprised of silica, those comprised of silicaand an inorganic compound other than silica and those comprised of suchas CaF₂, NaF, NaAlF₆ and MgF. Among them, specifically preferable is aporous particle comprised of a complex oxide of silica and an inorganiccompound other than silica. An inorganic compound other than silicaincludes one type or at least two types of such as Al₂O₃, B₂O₃, TiO₂,ZrO₂, SnO₂, CeO₂, P₂O₃, Sb₂O₃, MoO₃, ZnO₂ and WO₃. In such a porousparticle, mole ratio MO_(x)/SiO₂ is preferably in a range of 0.0001-1.0and more preferably of 0.001-0.3 when silica is represented by SiO₂ andan inorganic compound other than silica is represented by an equivalentoxide (MO_(x)). A porous particle having mole ratio MO_(x)/SiO₂ of lessthan 0.0001 is difficult to be prepared and the pore volume is small tounable preparation of a particle having a low refractive index. Further,when mole ratio MO_(x)/SiO₂ of a porous particle is over 1.0, the porevolume becomes large due to a small ratio of silica and it may befurther difficult to prepare a particle having a low refractive index.

A pore volume of such a porous particle is preferably in a range of0.1-1.5 ml/g and more preferably of 0.2-1.5 ml/g. When the pore volumeis less than 0.1 ml/g, a particle having a sufficiently decreasedrefractive index cannot be prepared, while, when it is over 1.5 ml/g,strength of a particle is decreased and strength of the obtained coverfilm may be decreased. Herein, the pore volume of such a porous particlecan be determined by a mercury pressurized impregnation method. Further,a content of a hollow particle includes such as a solvent, a gas and aporous substance which have been utilized at preparation of theparticle. In a solvent, such as a non-reacted substance of a particleprecursor which is utilized at hollow particle preparation and autilized catalyst may be contained. Further, a porous substance includesthose comprising compounds exemplified in the aforesaid porous particle.These contents may be those containing single component or mixture ofplural components.

As a manufacturing method of such hollow particles, a preparation methodof complex oxide colloidal particles, disclosed in paragraph Nos.[0010]-[0033] of JP-A No. 7-133105, is suitably applied.

The hollow particles thus obtained have a low refractive index, sinceinside of them are vacant, and the refractive index of the lowrefractive index layer of the present invention, in which the hollowparticles are employed, is preferably 1.30-1.50 and more preferably1.35-1.44.

The content of the hollow silica particles having an outer shell andporous or hollow inside is preferably 10-80% by weight and morepreferably 20-60% by weight based on the weight of the coating solutionfor the low refractive index layer.

(Tetraalkoxysilane Relating Compounds and Hydrolysis Products Thereof)

In the low refractive index layer of the present invention preferablycontains a tetraalkoxysilane relating compounds or a hydrolysis productthereof as a sol-gel material.

As a material for the low refractive index layer of the presentinvention, silicon oxides having an organic group, other than the aboveinorganic compounds, are preferably used. These compounds are called asol-gel material, and a metal alcolate, an organo-alkoxy metal compoundand a hydrolysis product thereof are applicable. Specifically preferableare an alkoxysilane (such as tetramethoxysilane and tetraethoxysilane),alkyltrialkoxysilane (such as methyltrimethoxysilane, andethyltrimethoxysilane), aryltrialkoxysilane (such asphenyltrimethoxysilane), dialkyldialkoxysilane and diaryldialkoxysilane.

The low refractive index layer employed in the present inventionpreferably contains the above silicon-containing compound and a silanecoupling agent.

Specific examples of a silane coupling agent includemethyltrimethoxysilane, methyltriethoxysilane,methyltrimethoxyethoxysilane, methyltriacetoxysilane,methyltributoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane,vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriacetoxysilane,vinyltrimethoxyethoxysilane, phenyltrimethoxysilane,phenyltriethoxysilane, phenyltriacetoxysilane.

Further, examples of a silane coupling agent having an doublysubstituted alkyl groups to silicon include: dimethyldimethoxysilane,phenylmethyldimethoxysilane, dimethyldiethoxysilane andphenylmethyldiethoxysilane.

Specific examples of a silane coupling agent include: KBM-303, KBM-403,KBM-402, KBM-403, KBM-1403, KBM-502, KBM-503, KBE-502, KBE-503, KBM-603,KBE-603, KBM-903, KBE-903, KBE-9103, KBM-802 and KBM-803.

It is preferable that these coupling agents have been preliminarilyhydrolyzed employing water in a necessary amount. When the silanecoupling agent is hydrolyzed, the surface of the above silicon oxideparticles and the silicon oxide having organic groups becomes easier toreact, whereby a stronger layer is formed. Further, it is preferable topreviously mix hydrolyzed silane coupling agents into a liquid coatingcomposition.

It is preferable that the low refractive index layer incorporatespolymers in an amount of 5-50% by weight. The above polymers exhibitfunctions such that particles are subjected to adhesion and thestructure of the above low refractive index layer is maintained. Theused amount of the polymers is controlled so that without filing voids,it is possible to maintain the strength of the low refractive indexlayer. The amount of the polymer is preferably 10-30% by weight based onthe total weight of the low refractive index layer. In order to achieveadhesion of particles employing polymers, it is preferable that (1)polymers are combined with surface processing agents of the particles,(2) a polymer shell is formed around a particle used as a core, or (3)polymers are employed as a binder of the particles.

Binder polymers are preferably polymers having saturated hydrocarbon orpolyether as a main chain, but is more preferably polymers havingsaturated hydrocarbon as a main chain. The above binder polymers arepreferably subjected to crosslinking. It is preferable that the polymershaving saturated hydrocarbon as a main chain is prepared employing apolymerization reaction of ethylenically unsaturated monomers. In orderto prepare crosslinked binder polymers, it is preferable to employ amonomer having at least two ethyleniccally unsaturated groups. Listed asexamples of monomers having at least two ethylenically unsaturatedgroups include: esters of polyalcohol with (meth)acrylic acid (forexample, ethylene glycol di(meth)acrylate, 1,4-dicyclohexane diacrylate,pentaerythritol tetra(meth)acrylate, pentaerythritol (meth)acrylate,trimethylolpropane tri(meth)acrylate, trimethylolethanetri(meth)acrylate, dipentaerythritol tetra(meth)acrylate,dipentaerythritol penta(meth)acrylate, pentaerythritolhexa(meth)acrylate, 1,2,3-cyclohexane tetramethacrylate, polyurethanepolyacrylate and polyester polyacrylate); vinylbenzene and derivativesthereof (for example, 1,4-divinylbenzene and 4-vinylbenzoicacid-2-acryloylethyl ester, and 1,4-divinylcyclohexane); vinylsulfones(for example, divinylsulfone); acrylamides (for example,methylenebisacrylamide); and methacrylamides.

The low refractive index layer employed in the present invention may bea low refractive index layer which is formed by crosslinking offluorine-containing resins (hereinafter referred to as“fluorine-containing resins prior to crosslinking”) which undergocrosslinking by heat or by irradiation of ionizing radiation.

Preferably listed as fluorine containing resins prior to crosslinkingare fluorine containing copolymers which are formed employing a fluorinecontaining vinyl monomer and a monomer which provides a crosslinkinggroup. Listed as specific examples of the above fluorine containingvinyl monomer units include: fluoroolefins (for example, fluoroethylene,vinylidene fluoride, tetrafluoroethylene, hexafluoroethylene,hexafluoropropylene and perfluoro-2,2-dimethyl-1,3-dioxol), partially orcompletely fluorinated alkyl ester derivatives of (meth)acrylic acid(for example, BISCOAT 6FM (produced by Osaka Organic Chemical IndustryLtd.) and M-2020 (produced by Daikin Industries, Ltd.), and completelyor partially fluorinated vinyl ethers. Listed as monomers to provide acrosslinking group are vinyl monomers having a crosslinking functionalgroup in the molecule, such as glycidyl methacrylate,vinyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, or vinylglycidyl ether, as well as vinyl monomers having a carboxyl group, ahydroxyl group, an amino group, or a sulfone group (for example,(meth)acrylic acid, methylol (meth)acrylate, hydroxyalkyl(meth)acrylate, allyl acrylate, hydroxyalkyl vinyl ether, andhydroxyalkyl allyl ether). JP-A Nos. 10-25388 and 10-147739 describethat a crosslinked structure is introduced into the latter compounds byadding compounds having a group which reacts with the functional groupin the polymer and at least one reacting group, after thecopolymerization. Listed as examples of the crosslinking group include:acryloyl, methacryloyl, isocyanate, epoxy, aziridine, oxazoline,aldehyde, carbonyl, hydrazine, carboxyl, methylol and activatedmethylene. When fluorine containing polymers undergo thermalcrosslinking due to the presence of a thermally reacting crosslinkinggroup or the combinations of an ethylenically unsaturated group withthermal radical generating agents or an epoxy group with a heatgenerating agent, the above polymers are of a heat curable type. On theother hand, in cases in which crosslinking undergoes by exposure toradiation (preferably ultraviolet radiation and electron beams)employing combinations of an ethylenically unsaturated group withphoto-radical generating agents or an epoxy group with photolyticallyacid generating agents, the polymers are of an ionizing radiationcurable type.

The used ratio of each monomer to form the fluorine containingcopolymers prior to coating is as follows. The ratio of fluorinecontaining vinyl monomers is preferably 20-70 mol %, but is morepreferably 40-70 mol %; the ratio of monomers which provide acrosslinking group is preferably 1-20 mol %, but is more preferably 5-20mol %, and the ratio of the other monomers simultaneously employed ispreferably 10-70 mol %, but is more preferably 10-50 mol %.

Each layer of the antireflection film may be formed via a coatingmethod, for example, a dip coat method, an air knife coat method, acurtain coat method, a roller coat method, a wire bar coat method, agravure coat method, or an extrusion coat method (U.S. Pat. No.2,681,294). Two or more layers may be applied simultaneously. The methodof simultaneous application is described in, for example, U.S. Pat. Nos.2,761,791, 2,941,898, 3,508,947, 3,526,528 and “Yuji Harasaki: CoatingEngineering, p. 253 (1973), published by Asakura Publishing Co., Ltd.”

The thickness of the low refractive index layer is preferably 50-200 nmand more preferably 60-150 nm.

<High Refractive Index Layer and Medium Refractive Index Layer>

In the present invention, a high refractive index layer is preferablyprovided between a transparent substrate and a low refractive indexlayer in order to reduce the reflectance. Further, to provide a mediumrefractive index layer between a transparent substrate and a highrefractive index layer is preferred with respect to reduction of thereflectance. A refractive index of a high refractive index layer ispreferably 1.55-2.30 and more preferably 1.57-2.20. A refractive indexof a medium refractive index layer is adjusted to be an intermediatevalue between a refractive index of a transparent support and arefractive index of a high refractive index layer. A refractive index ofa medium refractive index layer is preferably 1.55-1.80. The thicknessof each of a high refractive index layer and a medium refractive indexlayer is preferably 5 nm-1 μm, more preferably 10 nm-0.2 μm and mostpreferably 30 nm-0.1 μm. The haze of a high refractive index layer and amedium refractive index layer is preferably not more than 5%, morepreferably not more than 3% and most preferably not more than 1%. Thestrength of a high refractive index layer and a medium refractive indexlayer is preferably not less than H based on pencil hardness at aloading weight of 1 kg, more preferably not less than 2 H and mostpreferably not less than 3 H.

It is preferable that the medium and high refractive index layers usedin the present invention are formed in such a manner that a liquidcoating composition incorporating monomers or oligomers of organictitanium compounds represented by Formula (22) below, or hydrolyzedproducts thereof are coated and subsequently dried, and the resultingrefractive index is 1.55-2.5.Ti(OR₁)₄   Formula (22)wherein R₁ is an aliphatic hydrocarbon group having 1-8 carbon atoms,but is preferably an aliphatic hydrocarbon group having 1-4 carbonatoms. Further, in monomers or oligomers of organic titanium compoundsor hydrolyzed products thereof, the alkoxide group undergoes hydrolysisto form a crosslinked structure via reaction such as —Ti—O—Ti—, wherebya cured layer is formed.

Listed as prefered examples of monomers and oligomers of organictitanium compounds employed in the present invention include: Ti(OCH₃)₄,Ti(OC₂H₅)₄, Ti(O-n-C₃H₇)₄, Ti(O-i-C₃H₇)₄, Ti(O-n-C₄H₉)₄, dimers-decamersof Ti(O-n-C₃H₇)₄, dimers-decamers of Ti(O-i-C₃H₇)₄, dimers-decamers ofTi(O-n-C₄H₉)₄. These may be employed individually or in combinations ofat least two types. Of these, particularly preferred are Ti(O-n-C₃H₇)₄,Ti(O-i-C₃H₇)₄, Ti(O-n-C₄H₉)₄, dimers-decamers of Ti(O-n-C₃H₇)₄ anddimers-decamers of Ti(O-n-C₄H₉)₄.

The content of monomers and oligomers of organic titanium compoundsemployed in the present invention, as well as hydrolyzed productsthereof is preferably 50.0-98.0 weight % with respect to solidsincorporated in the liquid coating composition. The solid ratio is morepreferably 50-90 weight %, but is still more preferably 55-90 weight %.Other than these, it is preferable to incorporate polymers of organictitanium compounds (which are subjected to hydrolysis followed bycrosslinking) in a liquid coating composition, or to incorporatetitanium oxide particles.

The high refractive index and medium refractive index layers used in thepresent invention preferably incorporate metal oxide particles asmicroparticles and further preferably incorporate binder polymers.

In the above method of preparing liquid coating compositions, whenhydrolyzed/polymerized organic titanium compounds and metal oxideparticles are combined, the both strongly adhere to each other, wherebyit is possible to obtain a strong coating layer provided with hardnessand uniform layer flexibility.

The refractive index of metal oxide particles employed in the high andmedium refractive index layers is preferably 1.80-2.80, but is morepreferably 1.90-2.80. The weight average diameter of the primaryparticle of metal oxide particles is preferably 1-150 nm, is morepreferably 1-100 nm, but is most preferably 1-80 nm. The weight averagediameter of metal oxide particles in the layer is preferably 1-200 nm,is more preferably 5-150 nm, is still more preferably 10-100 nm, but ismost preferably 10-80 nm. Metal oxide particles at an average particlediameter of at least 20-30 nm are determined employing a lightscattering method, while the particles at a diameter of at most 20-30 nmare determined employing electron microscope images. The specificsurface area of metal oxide particles is preferably 10-400 m²/g as avalue determined employing the BET method, is more preferably 20-200m²/g, but is most preferably 30-150 m²/g.

Examples of metal oxide particles are metal oxides incorporating atleast one element selected from the group consisting of Ti, Zr, Sn, Sb,Cu, Fe, Mn, Pb, Cd, As, Cr, Hg, Zn, Al, Mg, Si, P, and S. Specificallylisted are titanium dioxide, (for example, rutile, rutile/anatase mixedcrystals, anatase, and amorphous structures), tin oxide, indium oxide,zinc oxide, and zirconium oxide. Of these, titanium oxide, tin oxide,and indium oxide are particularly preferred. Metal oxide particles arecomposed of these metals as a main component of oxides and are capableof incorporating other metals. Main component, as described herein,refers to the component of which content (in percent by weight) is themaximum in the particle composing components. Listed as examples ofother elements are Ti, Zr, Sn, Sb, Cu, Fe, Mn, Pb, Cd, As, Cr, Hg, Zn,Al, Mg, Si, P and S.

It is preferable that metal oxide particles are subjected to a surfacetreatment. It is possible to perform the surface treatment employinginorganic or organic compounds. Listed as examples of inorganiccompounds used for the surface treatment are alumina, silica, zirconiumoxide, and iron oxide. Of these, alumina and silica are preferred.Listed as examples of organic compounds used for the surface treatmentare polyol, alkanolamine, stearic acid, silane coupling agents, andtitanate coupling agents. Of these, silane coupling agents are mostpreferred.

The content of metal oxide particles in the high and medium refractiveindex layers is preferably 5-65 volume %, more preferably 10-60 volume %and still more preferably 20-55 volume %.

The above metal oxide particles are dispersed into a medium and fed toliquid coasting compositions to form a high refractive index layer and amedium refractive index layer. Preferably employed as dispersion mediumof metal oxide particles is a liquid at a boiling point of 60-170° C.Specific examples of dispersion media include water, alcohols (forexample, methanol, ethanol, isopropanol, butanol, and benzyl alcohol),ketones (for example, acetone, methyl ethyl ketone, methyl isobutylketone, and cyclohexanone), esters (for example, methyl acetate, ethylacetate, propyl acetate, butyl acetate, methyl formate, ethyl formate,propyl formate and butyl formate), aliphatic hydrocarbons (for example,hexane and cyclohexanone), halogenated hydrocarbons (for example,methylene chloride, chloroform, and carbon tetrachloride), aromatichydrocarbons (for example, benzene, toluene, and xylene), amides (forexample, dimethylformamide, diethylacetamide, and n-methylpyrrolidone),ethers (for example, diethyl ether, dioxane, and tetrahydrofuran), andether alcohols (for example, 1-methoxy-2-propanol). Of these,particularly preferred are toluene, xylene, methyl ethyl ketone, methylisobutyl ketone, cyclohexane and butanol.

Further, it is possible to disperse metal oxide particles into a mediumemploying a dispersing machine. Listed as examples of a dispersingmachine include: a sand grinder mill (for example, a bead mill withpins), a high speed impeller mill, a pebble mill, a roller mill, anattritor, and a colloid mill. Of these, particularly preferred are thesand grinder and the high speed impeller mill. Preliminary dispersionmay be performed. Listed as examples which are used for the preliminarydispersion include a ball mill, a three-roller mill, a kneader, and anextruder.

It is preferable to employ polymers having a crosslinked structure(hereinafter referred to as a crosslinked polymer) as a binder polymerin the high refractive index and medium refractive index layers. Listedas examples of the crosslinked polymers include: polymers having asaturated hydrocarbon chain such as polyolefin, polyether, polyurea,polyurethane, polyester, polyamine, polyamide and melamine resins. Ofthese, crosslinked products of polyolefin, polyether and polyurethaneare preferred, crosslinked products of polyolefin and polyether are morepreferred, and crosslinked products of polyolefin are most preferred.

Most preferred as monomers employed in the present invention are thosehaving at least two ethylenically unsaturated groups. Listed as thoseexamples include: esters of polyalcohols and (meth)acrylic acid (forexample, ethylene glycol di(meth)acrylate, 1,4-cyclohexane diacrylate,pentaerythritol tetra(meth)acrylate, pentaerythritol tri(meth)acrylate,trimethylolpropane tri(meth)acrylate, trimethylolethanetri(meth)acrylate, dipentaerythritol tetra(meth)acrylate,dipentaerythritol (meth)acrylate, pentaerythritol hexa(meth)acrylate,1,2,3-cyclohexane tetramethacrylate, polyurethane polyacrylate, andpolyester polyacrylate); vinylbenzne and derivatives thereof (forexample, 1,4-divinylbenzene, 4-vinyl-benzoic acid-2-acryloylethyl ester,and 1,4-divinylcyclohexane); vinylsulfones (for example,divinylsulfone); acrylamides (for example, methylenebisacrylamide); andmethacrylamides. Commercially available monomers having an anionic groupand monomers having an amino group or a quaternary ammonium group may beemployed. Listed as commercially available monomers having an anionicgroup which are preferably employed are KAYAMAR PM-21 and PM-2 (bothproduced by Nihon Kayaku Co., Ltd.); ANTOX MS-60, MS-2N, and MS-NH4 (allproduced by Nippon Nyukazai Co., Ltd.), ARONIX M-5000, M-6000, andM-8000 SERIES (all produced by Toagosei Chemical Industry Co., Ltd.);BISCOAT #2000 SERIES (produced by Osaka Organic Chemical Industry Ltd.);NEW FRONTIER GX-8289 (produced by Dai-ichi Kogyo Seiyaku Co., Ltd.); NKESTER CB-1 and A-SA (produced by Shin-Nakamura Chemical Co., Ltd.); andAR-100, MR-100, and MR-200 (produced by Daihachi Chemical Industry Co.,Ltd.). Listed as commercially available monomers having an amino groupor a quaternary ammonium group which are preferably employed are DMAA(produced by Osaka Organic Chemical Industry Ltd.); DMAEA and DMAPAA(produced by Kojin Co., Ltd.); BLENMER QA (produced by NOF Corp.), andNEW FRONTIER C-1615 (produced by Dai-ichi Kogyo Seiyaku Co., Ltd.).

It is possible to perform a polymerization reaction employing aphotopolymerization reaction or a thermal polymerization reaction. Thephotopolymerization reaction is particularly preferred. It is preferableto employ a polymerization initiator to perform the polymerizationreaction. For example, listed are thermal polymerization initiators andphotopolymerization initiators described below which are employed toform binder polymers of a hard coat layer.

A commercially available polymerization initiator may be used. Inaddition to the polymerization initiators, employed may be apolymerization promoter. The added amount of a polymerization initiatorand a polymerization promoter is preferably in the range of 0.2-10weight % based on the total weight of the monomer.

In the coating solution for each layer of the antireflection layer, apolymerization inhibitor, a leveling agent, a thickening agent, ananti-coloring agent, a UV-absorber, a silane coupling agent, anantistatic agent or an adhering agent may be incorporated, in additionto the above-mentioned components (metal oxide particles, a polymer, adispersion medium, a polymerization initiator and a polymerizationpromoter).

After the high-medium refractive index layer and the low refractiveindex layer are applied, irradiation with actinic rays is preferablycarried out in order to promote hydrolysis or curing of the compositioncontaining a metal alkoxide. More preferable is to carry out irradiationafter application of each layer.

The actinic radiation usable in the present invention includes, forexample, ultraviolet ray (UV ray), electron beam and γ-ray, and theactinic ray is not limited as long as it activates a compound. However,more preferable is ultraviolet ray or electron beam. The UV ray isspecifically preferred since handling is easy and a high level of energycan be easily obtained. Any light source capable of generating UV rayscan be used as the light source of the UV ray for causingphoto-polymerization of UV ray curable compound. For example, it ispossible to use the low pressure mercury lamp, intermediate pressuremercury lamp, high pressure mercury lamp, ultra-high pressure mercurylamp, carbon arc light, metal halide lamp and xenon lamp. Further, ArFexcimer laser, KrF excimer laser, excimer lamp and synchrotron radiationcan also be used. The conditions on irradiation differs according toeach type. The preferred amount of irradiation is preferably 20-10000mJ/cm², more preferably 100-2000 mJ/cm² and specifically preferably400-2000 mJ/cm².

(Polarizing Plate)

The polarizing plate of the present invention and the liquid crystaldisplay of the present invention, employing the polarizing plate willnow be described.

<Polarizing Film>

A polarizer (polarizing film), which is a main component of a polarizingplate, is the element which only transmits light having a polarizationplane in the definite direction. The representative polarizer which iscurrently known is a polyvinyl alcohol based polarizing film, whichinclude two types, one which is prepared by dying a polyvinyl alcoholbased film with iodine and the other which is prepared by dying the samewith a dichroic dye.

It is preferable that the polarizing film is formed employingethylene-modified polyvinyl alcohol having an ethylene unit content of1-4 mol %, a degree of polymerization of 2,000-4,000 and asaponification ratio of 99.0-99.99 mol %. The cutting temperature inhot-water of the film is preferably 66-73° C. Further, in order todecrease color spots, it is more preferable that the difference betweenthe hot water cutting temperatures of the two points 5 cm apart in theTD direction of the film is at most 1° C. Further, in order to decreasecolor spots, it is still more preferable that the difference between thehot water cutting temperatures of the two points 1 cm apart in the TDdirection is at most 0.5° C. Further, it is particularly preferable thatthe film thickness is 10-50 μm, in order to decrease color spots.

Employed as the ethylene-modified polyvinyl alcohol (being theethylene-modified PVA) is prepared in such a manner that anethylene-vinyl ester polymer, prepared by copolymerizing ethylene andvinyl ester based monomers, is saponified, whereby vinyl ester units arechanged to vinyl alcohol units. Examples of a vinyl ester monomerinclude: vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate,vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivaliate, andversatic acid vinyl esters. Of these, it is preferable to employ vinylacetate.

The content (being the copolymerized amount of ethylene) ethylene unitsin the ethylene-modified PVA is commonly 1-4 mol %, is preferably 1.5-3mol %, but is more preferably 2-3 mol %. When the content of theethylene units is less than 1 mol %, the polarizing performance, thedurability enhancing effects, and color spot decreasing effects of theresulting polarizing film are undesirably degraded. On the other hand,when it exceeds 4 mol %, affinity of the ethylene-modified PVA to wateris reduced, whereby the uniformity the film surface is undesirablydegraded to tend to cause the formation of color spots of the polarizingfilm.

Further, during copolymerization of ethylene with vinyl ester basedmonomers, if desired, it is possible to copolymerize copolymerizablemonomers in the range (at a ratio of preferably at most 15 mol %, butmore preferably at most 5 mol %) in which the effects of the presentinvention is adversely affected.

Examples of such copolymerizable monomers with vinyl ester monomersinclude olefins having 3-30 carbon atoms such as propylene, 1-butene, orisobutene; acrylic acid and salts thereof; acrylic acid esters such asmethyl acrylate, ethyl acrylate, n-propyl acrylate, i-propyl acrylate,n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexylacrylate, dodecyl acrylate, or octadecyl acrylate; methacrylic acid andsalts thereof; methacrylic acid esters such as methyl methacrylate,ethyl methacrylate, n-propyl methacrylate, i-propyl methacrylate,n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexylmethacrylate, dodecyl methacrylate, or octadecyl methacrylate;acrylamide derivatives such as acrylamide, N-methylacrylamide,N-ethylacrylamide, N,N-dimethylacrylamide, diacetoneacrylamide,acrylamide propane sulfinic acid and salts thereof,acrylamidopropyldimethylanine and salts thereof, N-methylol acrylamideand derivatives thereof; methacrylamide derivatives such asmethacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide,methacrylamidopropane sulfonic acid and salts thereof,methacrylamidopropyldimethylamine and salts thereof, or N-methylolmethacrylamide and derivatives thereof; N-vinylamides such asN-vinylformamide, N-vinylacetamide, or n-vinylpyrrolidone; vinyl etherssuch as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether,i-propyl vinyl ether, n-butyl vinyl ether, i-butyl vinyl ether, t-butylvinyl ether, dodecyl vinyl ether, or stearyl vinyl ether; nitriles suchas acrylonitrile or methacrylonitrile; halogenated vinyls such as vinylchloride, vinylidene chloride, vinyl fluoride, or vinylidene fluoride;allyl compounds such as allyl acetate or allyl chloride; maleic acid,and salts and esters thereof; itaconic acid, and salts and estersthereof; vinylsilyl compounds such as vinylmethoxysilane; andN-vinylamides such as isopropenyl acetate, N-vinylformamide,N-vinylacetamide, or N-vinylpyrrolidone.

The degree of polymerization of ethylene-modified PVA composing thepolarizer and of PVA of the polarizing film is commonly 2,000-4,000, ispreferably 2,200-3,500, but is more preferably 2,500-3,000 in terms ofpolarizing performance and durability. When the degree of polymerizationof ethylene-modified PVA is less than 2,000, the polarizing performanceand durability of the polarizing film are undesirably degraded. On theother hand, the degree of polymerization of at most 4,000 is preferredsince color spots of the polarizer are hardly formed.

The degree of polymerization of the ethylene-modified PVA refers to theweight average polymerization degree. This weight average polymerizationdegree is determined by means of GPC measurement at 40° C. employinghexafluoroisopropanol (HFIP) added with 20 mmol/liter of sodiumtrifluoroactate in the moving phase employing monodispersed PMMA as astandard product.

In view of polarization performance and durability of a polarizing film,the ratio of saponification of the ethylene-modified PVA constitutingthe polarizer is preferably 99.0-99.99 mol %, is more preferably99.9-99.99 mol %, but is most preferably 99.95-99.99 mol %.

Employed as methods to produce a ethylene-modified film, other than afilm forming method based on a melt extrusion system employingwater-containing ethylene-modified PVA, include, using anethylene-modified PVA solution prepared by dissolving ethylene-modifiedPVA in solvents, a casting method, a wet system film forming method(ejected into poor solvents), a gel film forming method (after anethylene-modified PVA solution is temporality cooled and gelled,solvents are removed via extraction and an ethylene-modified PVA film isprepared), as well as methods of combinations of these. Of these, inview of obtaining an excellent ethylene-modified PVA film, preferred arethe casting method and the melt extrusion method. The resultingethylene-modified PVA film is, if necessary, dried and thermallytreated.

Examples of a solvent which dissolves the ethylene-modified PVA employedduring production of ethylene-modified PVA film include:dimethylsulfoxide, dimethylformamide, dimethylacetamide,N-methylpyrrolidone, ethylene glycol, glycerin, propylene glycol,triethylene glycol, tetraethylene glycol, trimethylolpropane,ethylenediamine, diethylenetriamine, glycerin and water. These may beemployed alone or in combination of two or more. Of these, suitablyemployed is dimethylsulfoxide, water, or a mixed solvent of glycerin andwater.

The ratio of ethylene-modified PVA, incorporated in an ethylene-modifiedPVA solution or water-containing ethylene-modified PVA employed duringproduction of the ethylene-modified film, varies depending on the degreeof polymerization of the ethylene-modified PVA, but is commonly 20-70%by weight, is preferably 25-60% by weight, but is more preferablyappropriately 30-55% by weight, but is most preferably 35-50 by weight.When the ratio of the ethylene-modified PVA exceeds 70% by weight,viscosity of the ethylene-modified PVA solution or the water-containingethylene-modified PVA becomes excessively high, whereby it becomesdifficult to prepare a film without foreign matter and defects due todifficult filtration and defoaming. On the other hand, when the ratio ofthe ethylene-modified PVA is at most 20% by weight, the viscosity of theethylene-modified PVA solution or the water-containing ethylene-modifiedPVA becomes excessively low, whereby it becomes difficult to prepare aPVA film at the targeted thickness. Further, if desired, plasticizers,surfactants, and dichroic dyes may be incorporated in the aboveethylene-modified PVA solution or water-containing ethylene-modifiedPVA.

During production of the ethylene-modified PVA film, it is preferable toincorporate polyalcohols as a plasticizer. Examples of polyalcoholsinclude ethylene glycol, glycerin, propylene glycol, diethylene glycol,diglycerin, triethylene glycol, tetraethylene glycol, andtrimethylolpropane. These may be employed individually or incombinations of at least two types. Of these, in view of orientationenhancement effects, diglycerin, ethylene glycol, and glycerin arepreferable.

The added amount of polyalcohols is preferably 1-30 parts by weight withrespect to 100 parts by weight of the ethylene-modified PVA, is morepreferably 3-25 parts by weight, but is most preferably 5-20 parts byweight. When the added amount is less than 1 part by weight, dyingproperties and orientation properties are occasionally degraded, whilewhen it exceeds 30 parts by weight, the ethylene-modified film becomesexcessively flexible, whereby handling properties tend to be degraded.

During production of the ethylene-modified PVA film, it is preferable toincorporate a surfactant. The types of surfactants are not particularlylimited, but nonionic or cationic surfactants are preferred. Examples ofsuitable anionic surfactants include: carboxylic acid surfactants suchas potassium laurate, sulfuric acid ester surfactants such as octylsulfate, and sulfonic acid surfactants such as dodecylbenznenesulfonate. Examples of suitable nonionic surfactants include alkyl ethersurfactants such as polyoxyethylene oleyl ether; alkyl phenyl ethersurfactants such as polyoxyethylene octyl phenyl ether surfactants;alkyl ester surfactants such as polyoxyethylenelaurate; alkylaminesurfactants such as polyoxyethylene lauryl aminoether; alkylamidesurfactants such as polyoxyethylene lauric acid amide; polypropyleneglycol ether surfactants such as polyoxyethylene polyoxypropylene ether;alkanol amide surfactants such as oleic acid diethanolamide; and allylphenyl ether surfactants such as polyoxyalkylene phenyl ether. Thesesurfactants may be employed individually or in combinations of at leasttwo types.

The added amount of surfactants is preferably 0.01-1 part by weight withrespect to 100 parts by weight of the ethylene-modified PVA, is morepreferably 0.02-0.5 part by weight, but is most preferably 0.05-0.3 partby weight. When the added amount is less than 0.01 part by weight,effects to improve film casting properties and peeling properties arehardly exhibited, while when it exceeds 1 part by weight, surfactantsare dissolved out onto the surface of the ethylene-modified PVA film toresult in blocking, whereby handling properties tend to be degraded.

The hot-water cutting temperature of the ethylene-modified PVA film ispreferably 66-73° C., is more preferably 68-73° C., but is mostpreferably 70 -73° C. When the hot-water cutting temperature of theethylene-modified PVA film is less than 66° C., a state occurs in whicha film, which starts dissolution, is stretched whereby the polarizationperformance becomes insufficient due to reduced tendency of molecularorientation. On the other hand, when the hot-water cutting temperatureis 73° C. or more, the film tends not to be stretched, whereby thepolarization performance of the polarizing film is undesirably degraded.When the ethylene-modified PVA film is dried and thermally treated, itis possible to control the hot-water cutting temperature of the film byvarying the temperature and time of the above treatments.

The thickness of the ethylene-modified PVA film employed to prepare apolarizer is preferably 10-80 μm, more preferably 10-50 μm and stillmore preferably 20-40 μm. When the thickness is more than 10 μm, uniformstretching is easy, whereby color spotting of the polarizing film tendsnot to occur. On the other hand, when the thickness does not exceeds 80μm, more preferably does not exceed 50 μm, during production of apolarizing film via uniaxial stretching of the ethylene-modified PVAfilm, the variation of thickness due to neck-in at the edge tends not tooccur, whereby color spotting of the polarizing film becomes lessappearing.

Further, to produce a polarizing film employing an ethylene-modified PVAfilm, for example, the ethylene-modified PVA film may be dyed,uniaxially stretched, fixed and dried, and, if desired, thermallytreated. The order of the dying, uniaxial stretching, and fixing is notparticularly limited. Further, the uniaxial stretching may be repeatedtwice or more.

Dying may be performed at any time such as prior to uniaxial stretching,during uniaxial stretching, or after uniaxial stretching. Employed asdyes for dying are dichroic dyes such as iodine-potassium iodide; DirectBlack 17, 19, and 154; Direct Brown 44, 106, 195, 210, and 223; DirectRed 2, 23, 28, 31, 37, 39, 79, 81, 240, 242, and 247; Direct Blue 1, 15,22, 78, 90, 98, 151, 168, 202, 236, 249, and 270; Direct Violet 9, 12,51, and 98; Direct Green 1 and 85; Direct Yellow 8, 12, 44, 86, and 87;and Direct Orange 26, 39, 106, and 107. These may be employedindividually or in combinations of at least two types. Dying is commonlyperformed by immersing a PVA film into a solution incorporating theabove dyes. Alternatively, the above dyes may be blended into a PVA filmduring casting. The above dying conditions and methods are notparticularly limited.

It is possible to conduct uniaxial stretching employing either a wetstretching method or a dry heat stretching method, and in heated water(in a solution containing the above-mentioned dyes or in a fixing bathwhich will be described below) or in air employing an ethylene-modifiedPVA film which absorbed water. The temperature during stretching is notparticularly limited, however, when the ethylene-modified PVA film isstretched in heated water (being wet system stretching), the stretchingtemperature is preferably 30-90° C., while in the case of dry heatstretching, it is preferably 50-180° C. The stretching factor (the totalstretching factor in the case of multistage uniaxial stretching) ispreferably 4 or more with respect to polarization performance of thepolarizing film, but is most preferably 5 or more. The upper limit ofthe stretching factor is not particularly limited, however, thestretching factor is preferably 8 or less, since uniform stretching isreadily performed. The film thickness after stretched is preferably 2-20μm, but is most preferably 10-20 μm.

To strengthen adsorption of the above dyes onto the ethylene-modifiedPVA film, a fixing treatment is frequently conducted. Commonly, boricacid and/or boron compounds are added to a treatment bath employed forthe fixing treatment. Alternatively, if desired, iodine compounds may beadded in the treatment bath.

Drying of a prepared polarizer is preferably performed between 30-150°C., but is more preferably performed between 50-150° C.

An optically transparent protective layer, exhibiting desired mechanicalstrength, is adhered to one or both sides of the polarizer prepared asabove to prepare a polarizing plate. Listed as adhesives for the aboveadhesion may be a PVA adhesive and an urethane adhesive. Of these, a PVAadhesive is preferable.

The polarizing plate can be produced by a usual method. It is preferablethat the back surface of the cellulose ester film of the presentinvention is subjected to the alkali saponification treatment and ispasted to at least one surface of a polarizing film using an aqueoussolution of completely saponified polyvinyl alcohol, the polarizing filmbeing prepared by immersing a polyvinyl alcohol film in an iodinesolution, followed by stretching the film. On the other surface of thepolarizing film, the cellulose ester film of the present invention maybe provided or other polarizing plate protective film may be provided.As the polarizing plate protective film other than the cellulose esterfilm of the present invention, a cellulose ester film available on themarket can be employed. Examples of a cellulose ester film available onthe market include: KC8UX2M, KC4UX, KC5UX, KC4UY, KC4FR, KC8UY, KC12UR,KC8UCR-3, KC8UCR-4, KC8UY-HA and KC8UX-RHA (each manufactured by KonicaMinolta Opto, Inc.), FUJITAC TD80UF, FUJITAC T80UZ, FUJITAC T40UZ and anantireflection film (FUJI FILM CV CLEAR VIEW UA, produced by Fuji PhotoFilm Co., Ltd.).

For example, polarizing plate having the following combinations arepossible:

-   Cellulose ester film of the present invention (80    μm)/polarizer/KC8UX-RHA-   Cellulose ester film of the present invention (40    μm)/polarizer/KC8UX-RHA-   Cellulose ester film of the present invention (80    μm)/polarizer/KC8UCR-5-   Cellulose ester film of the present invention (40    μm)/polarizer/KC8UCR-5-   Cellulose ester film of the present invention (80    μm)/polarizer/KC4UY-   Cellulose ester film of the present invention (40    μm)/polarizer/KC4UY-   Cellulose ester film of the present invention (80    μm)/polarizer/KC5UX-   Cellulose ester film of the present invention (40    μm)/polarizer/KC5UX-   Cellulose ester film of the present invention (80    μm)/polarizer/FUJITAC TD80UF-   Cellulose ester film of the present invention (40    μm)/polarizer/FUJITAC TD80UF-   Cellulose ester film of the present invention (80    μm)/polarizer/FUJITAC T40UZ-   Cellulose ester film of the present invention (40    μm)/polarizer/FUJITAC T40UZ-   Cellulose ester film of the present invention (80 μm)/polarizer/FUJI    FILM CV CLEAR VIEW UA-   Cellulose ester film of the present invention (40 μm)/polarizer/FUJI    FILM CV CLEAR VIEW UA

The polarizing plate protective film provided on the other surface ofthe polarizing film preferably has a hard coat layer or an antiglarelayer each having a thickness of 8-20 μm. Preferably employed is apolarizing plate protective film having a hard coat layer or anantiglare layer each being disclosed, for example, in JP-A Nos.2003-114333, 2004-203009, 2004-354699 or 2004-354828. Further,preferable is to have an antireflection layer containing a lowrefractive index layer on the hard coat layer or the antiglare layer,and the low refractive index layer preferably contains theabove-mentioned hollow particles.

Alternatively, it is also preferable to use a polarizing plateprotective film which also serves as an optical compensation film havingan optical anisotropic layer formed by orientating a liquid crystalcompound such as a discotic liquid crystal, a rod-shaped liquid crystalor a cholesteric liquid crystal. For example, the optical anisotropiclayer can be formed by the method described in JP-A No. 2003-98348. Thepolarizing plate superior in the flatness and having a stable viewingangle enlarging effect can be obtained by the use of such the film incombination with the optical film of the present invention. Moreover, afilm of a cyclic olefin resin, an acryl resin, a polyester resin or apolycarbonate resin may be used as the polarizing plate protective filmon the other surface of the polarizing plate. In such the case, the filmis preferably pasted with the polarizing plate through a suitableadhering treatment because such the film shows low suitability forsaponification treatment.

The polarizing film is stretched in one direction (usually in thelongitudinal direction). Therefore, when a polarizing plate is keptunder a high temperature and high humidity condition, the polarizingfilm shrinks in the stretching direction, usually in the longitudinaldirection, and expands in the direction orthogonal to the stretchingdirection, usually in the transverse direction. The expansion andshrinkage of the polarizing plate is larger when the polarizing plateprotective film is thinner. Specifically the shrinkage in thelongitudinal direction is larger. It is important to inhibit theexpansion and shrinkage of the film in the casting direction because thestretching direction of the polarizing film is usually the same as thecasting direction (MD direction) of the polarizing plate protectivefilm. The cellulose ester film of the present invention is superior inthe dimensional stability, accordingly, it is suitably employed as apolarizing plate protective film.

A polarizing plate may be constituted by pasting a polarizing plateprotective film on one surface of the polarizing plate and a separablefilm on the other surface. The polarizing plate protective film and theseparable film are employed for protecting the polarizing plate in thecourse of forwarding and inspection of the product. In this case, theprotective film is pasted onto the surface of the polarizing plateopposite to the surface to be pasted with the liquid crystal cell forprotecting the surface of the polarizing plate. A separable film isemployed for covering the adhesive layer for pasting the polarizingplate to the liquid crystal cell and applied onto the surface of thepolarizing plate to be pasted with the liquid crystal cell.

(In-Plane Switching Mode Liquid Crystal Display)

The liquid crystal display having superior visibility and enlargedviewing angle according to the present invention can be produced byincorporation of the polarizing plate of the present invention into anIPS mode liquid crystal display available on the market.

The in-plane switching mode liquid crystal display of the presentinvention includes a fringe-field switching (FFS) mode liquid crystaldisplay; therefore, the polarizing plate of the present invention canalso be incorporated in the FFS mode liquid crystal display and canexhibit the same effect as that in the case of the IPS (In PlaneSwitching) mode liquid crystal display.

In a liquid crystal display, an upper side polarizing film and a lowerside polarizing film are provided on a pair of substrates provided inthe upper side and the lower side of the liquid crystal cell for drivingthe display. It is preferable that the cellulose ester film of thepresent invention is provided between the upper substrate and the upperside polarizing film or between the lower substrate and the lower sidepolarizing film, or, alternatively, the cellulose ester film of thepresent invention is provided between the upper substrate and the upperside polarizing film and between the lower substrate and the lower sidepolarizing film.

EXAMPLES

The present invention will now be detailed with reference to examples,however the present invention is not limited thereto.

Example 1

<Synthesis of Polymer X>

Charged into a glass flask equipped with a stirrer, two drippingfunnels, a gas feeding tube, and a thermometer were 40 g of a mixture ofMonomers Xa and Xb of the type and ratio described in Table 1, 2 g ofmercaptopropionic acid as a chain transfer agent, and 30 g of toluene.The resulting mixture was heated to 90° C. Thereafter, the mixture ofMonomers Xa and Xb of the type and ratio described in Table 1 wasdripped over 3 hours from one dripping funnel, while 0.4 g ofazobisisobutyronitrile dissolved in 14 g of toluene was simultaneouslydripped from the other dripping funnel over 3 hours. Thereafter, 0.6 gof azobisisobutyronitrile, dissolved in 56 g of toluene, was drippedover 2 hours, and reaction was performed for an additional 2 hours,whereby Polymers X1—X5 were prepared. The weight average molecularweight of each of above Polymers X1—X5, as shown in Table 1, wasdetermined employing the method described below. The polymers havingdifferent molecular weights were prepared by varying the added amount ofmercaptopropionic acid as a chain transfer agent and the adding rate ofazobisisobutyronitrile.

MA, MMA, HEA, and HEMA, described in Table 1, are abbreviations of thefollowing compounds.

MA: methyl acrylate

MMA: methyl methacrylate

HEA: 2-hydroxyethyl acrylate

HEMA: 2-hydroxyethyl methacrylate

(Determination of Molecular Weight)

The weight average molecular weight was determined employinggel-permeation chromatography.

Measurement conditions follow.

Solvent: methylene chloride

Columns: SHODEX K806, K805, and K803G (produced by Showa Denko K. K.,employed by connecting three columns)

Column temperature: 25° C.

Sample concentration: 0.1% by weight

Detector: RI Model 504 (produced by GL Science Co.)

Pump: L6000 (produced by Hitachi, Ltd.)

Flow rate: 1.0 ml/minute

Calibration curve: a calibration curve based on 13 samples of standardPOLYSTYRENE STK standard POLYSTYRENE (produced by TOSOH Corp.) at an Mwof 500-1,000,000 was employed. Thirteen samples at an almost equalinterval were employed.

<Synthesis of Polymer Y>

Block polymerization was carried out based on the polymerization methoddescribed in JP-A No. 2000-128911. Namely, charged into a flask, fittedwith a stirrer, a nitrogen gas feeding pipe, a thermometer, a charginginlet, and a refluxing cooling pipe, was methyl acrylate or methylmethacrylate as Monomer Ya, and the ambient atmosphere in the flask wasreplaced with nitrogen gas, and thioglycerol, as described below, wasadded while stirring. After the addition of thioglycerol, polymerizationwas carried out for 4 hours by appropriately changing the temperature ofthe reactants. Thereafter, the reactants were cooled to room temperatureand polymerization was terminated by the addition of a 20 parts byweight of a 5% by weight benzoquinone tetrahydrofuran solution, wherebythe polymerization was terminated. The reaction products weretransferred to an evaporator and tetrahydrofuran, residual monomers andresidual thioglycerol were removed at 80° C. under vacuum, wherebyPolymers Y1—Y4, described in Table 1, were prepared. The weight averagemolecular weight of each of above Polymers Y1—Y4 was determinedemploying the measurement method described above, and is shown in Table1.

Methyl acrylate or methyl methacrylate 100 parts by weight

Thioglycerol 5 parts by weight TABLE 1 Polymer X: -(Xa)m-(Xb)n-(Xc)p-(m + n + p = 100) Weight Xa Xb Xc Average Monomer Monomer MonomerMonomer Monomer Monomer Molecular Polymer X Type Ratio:m Type Ratio:nType Ratio:p Weight Polymer X1 MMA 80 HEA 10 — — 5000 MA 10 Polymer X2MMA 80 HEA 20 — — 5000 Polymer X3 MMA 80 HEMA 20 — — 5000 Polymer X4 MMA80 HEA 20 — — 30000 Polymer X5 MMA 95 HEMA 5 — — 2000 Polymer Y:-(Ya)k-(Yb)q- (k + q = 100) Weight Ya Yb Average Monomer Monomer MonomerMonomer Molecular Polymer Y Type Ratio:k Type Ratio:q Weight Polymer Y1MA 100 — — 1000 Polymer Y2 MMA 100 — — 1000 Polymer Y3 MA 100 — — 500Polymer Y4 MA 100 — — 3000<Synthesis Example of Polymer UV Absorber P-1>

Synthesis of 2(2′-hydroxy-5′-t-butyl-phenyl)-5-carboxylicacid-(2-methacryloyloxy)ethyl ester-2H-benzotriazole (ExemplifiedCompound MUV-19) was carried out based on the method described below.

Dissolved in 160 ml of water was 20.0 g of 3-nitro-4-amino-benzoic acid,and 43 ml of concentrated hydrochloric acid was added. After adding 8.0g of sodium nitrite dissolved in 20 ml of water at 0° C., the resultingmixture was stirred for 2 hours while maintaining the temperature at 0°C. Dripped into the resulting solution at 0° C. was 17.3 g of4-t-butylphenol dissolved in 50 ml of water and 100 ml of water whilemaintaining alkalinity by the addition of potassium carbonate. Theresulting solution was stirred at 0° C. for one hour and for anadditional hour at room temperature. The reaction solution was acidifiedby the addition of hydrochloric acid and the resulting precipitates werecollected via filtration, and subsequently washed well with water.

Precipitates collected via filtration were dissolved in 500 ml of a 1mol/L aqueous NaOH solution. After adding 35 g of zinc powder, 110 g ofa 40% aqueous NaOH solution was dripped. After dripping, stirring wascarried out for about 2 hours, followed by filtration and water washing.The filtrate was neutralized by the addition of hydrochloric acid. Theresulting precipitates were collected via filtration, washed with waterand dried. Thereafter, re-crystallization was conducted employing asolvent mixture of ethyl acetate and acetone, whereby2(2′-hydroxy-5′-t-butyl-phenyl)-5-carboxylic acid-2H-benzotriazole wasprepared.

Subsequently added to 100 ml of toluene were 10.0 g of2(2′-hydroxy-5′-t-butyl-phenyl)-5-carboxylic acid-2H-benzotriazole, 0.1g of hydroquinone, 4.6 g of 2-hydroxyethyl methacrylate, and 0.5 g ofp-toluenesulfonic acid, and the resulting mixture was refluxed for 10hours in a flask fitted with an ester pipe while heated. The reactionsolution was poured into water and precipitated crystals were collectedvia filtration, washed with water, dried, and recrystallized via ethylacetate, whereby 2(2′-hydroxy-5′-t-butyl-phenyl)-5-carboxylicacid-(2-methacryloyloxy)ethyl ester-2H-benzotriazole, which wasExemplified Compound MUV-19, was prepared.

Subsequently, a copolymer (being Polymer UV Absorber P-1) of2(2′-hydroxy-5′-t-butyl-phenyl)-5-carboxylicacid-(2-methacryloyloxy)ethyl ester-2H-benzotriazole with methylmethacrylate was synthesized based on the following method.

Added to 80 ml of tetrahydrofuran were 4.0 g of2(2′-hydroxy-5′-t-butyl-phenyl)-5-carboxylicacid-(2-methacryloyloxy)ethyl ester-2H-benzotriazole, synthesized asabove, and 6.0 g of methyl methacrylate, followed by the addition of1.14 g of azoisobutyronitrile. The resulting mixture was refluxed, whileheated, for 9 hours under a nitrogen atmosphere. After distilling offtetrahydrofuran under vacuum, the resulting products were re-dissolvedin tetrahydrofuran, and the resulting solution was dripped into anexcessive amount of methanol. The resulting precipitates were collectedvia filtration and dried at 40° C. under vacuum, whereby 9.1 g of a graypowdered polymer, which corresponded to Polymer UV Absorber P-1, wasprepared. The number average molecular weight of the resulting polymerwas confirmed to be 4,500, according to the GPC analysis employing thestandard polystyrene. Further, the above copolymer was identified as acopolymer of 2(2′-hydroxy-5′-t-butyl-phenyl)-5-carboxylicacid-(2-methacryloyloxy)ethyl ester-2H-benzotriazole with methylmethacrylate. The composition of the above copolymer was2(2′-hydroxy-5′-t-butyl-phenyl)-5-carboxylicacid-(2-methacryloyloxy)ethyl ester-2H-benzotriazole:methyl methacrylatewas approximately 40:60. (Preparation of Cellulose Ester Film 1)(Preparation of Dope) Cellulose Triacetate (at a 100 parts by weightsubstitution degree of an acetyl group of 2.92, an Mn of 100,000 and anMw of 220,000, and an Mw/Mn of 2.2) Additive 1 12 parts by weightAdditive 2 5 parts by weight Polymer UV Absorber P-1 3 parts by weightMinute silicon oxide particles 0.1 parts by weight (AEROSIL R972,produced by Nippon Aerosol Co., Ltd.) Methylene chloride 440 parts byweight Ethanol 40 parts by weight(Casting of Cellulose Ester Film)

The above dope was prepared, filtered employing FINE MET NF, produced byNippon Seisen Co. Ltd. and subsequently, at 22° C., cast onto astainless steel band support to reach a width of 2 m, employing a beltcasting apparatus. The solvents in the cast dope were evaporated on thestainless steel band so that the residual solvent amount reached 100%,and the resulting web was peeled from the stainless steel band at apeeling tension of 162 Newton/m, and was then slit to a width of 1.6 m.Thereafter, drying was performed at a drying temperature of 136° C.while stretched at a factor of 1.1 was performed in the traversedirection employing a tenter. During this operation, the residualsolvent amount was 10% at the beginning of stretching employing thetenter. After stretching by the tenter, the heating treatment, ambientair replacement, and pressing treatment, as described below, werecarried out, whereby drying was completed. The resulting film was slitto a width of 1.5 m, and knurling, at a width of 10 mm and a height of 5μm, was applied to both edges of the film. Subsequently, the resultingfilm was wound onto a core at an inner diameter of 6 inches at aninitial tension of 220 N/m and a final tension of 110 N/m, wherebyCellulose Ester Film 1, described in Table 2, was prepared. Thestretching factor in the MD direction, calculated based on the rotationrate of the stainless steel band support and the driving rate of thetenter was 1.1. The residual solvent amount, the thickness, and the rolllength of each cellulose ester film were 0.1%, 80 μm, and 3,000 m,respectively.

After stretching by a tenter, the web was dried by drying 105° C. airflow in a conveying drying process in which a plurality rollers wasvertically staggered was so that the residual solvents reached 0.3% byweight. Thereafter, the resulting film was thermally treated for 20minutes in an ambience at 135° C. and an ambient air replacementfrequency of 25 times/hour. During the above treatment, a pressure of 10kPa in the thickness direction was applied to the film employing niprollers arranged as a multistage. Subsequently, the film was cooled toroom temperature and wound whereby Cellulose Ester Film 1 was prepared.

Subsequently, Cellulose Ester Films 2-39 were prepared in the samemanner as Cellulose Ester Film 1, except that the type and amount ofadditives, the film thickness, the heat treatment temperature, theambient air replacement frequency, and the presence or absence of thepressing treatment were changed to the conditions described in Table 2,and the free volume radius as well as the half-value width wasregulated.

The above ambient air replacement frequency of the heating process isthe frequency represented by the following formula in which thefrequency per unit time of replacement of the ambience to fresh air isobtained.Ambient Air Replacement Frequency=FA/V (times/hour) wherein V (m ²)represents the capacity of the heat treatment room and FA (m ²/hour)represents the blown amount of fresh air.

The retardation value of each of resulting Cellulose Ester Films 1-39was determined employing the following method.

(Measurement of Retardations Ro and Rt)

Three-dimensional refractive indices at a wavelength of 590 nm of eachof Cellulose Ester Films 1-29 were determined at 10 positions at 23° C.and 55% relative humidity, employing an automatic birefringence analyzer(KOBRA-21ADH, produced by Oji Scientific Instruments) and refractiveindices nx, ny, and nz were obtained. In-plane direction retardation Rowas obtained based on Formula (1), while thickness direction retardationRt was obtained based on Formula (2). Determination was carried out atten positions and the average value was obtained.Ro=(nx−ny)×d   Formula (a)Rt=((nx+ny)/2−nz)×d   Formula (b)wherein Ro represents the in-plane retardation value of the film, Rtrepresents the retardation value in the thickness direction of the film,nx represents the refractive index in the in-plane delayed phase axisdirection of the film, ny represents the refractive index of thein-plane advanced phase axis direction of the film, and nz representsthe refractive index of in the thickness direction of the film, and drepresents the thickness (nm) of the film.

Table 2 shows the above evaluation results. TABLE 2 Cellulose Free Half-Ester Pressing Volume Value Film Additive 1 Additive 2 UV TreatmentRadius Width Ro Rt No. Type *1 Type *1 Absorber *2 *3 *4 (kPa) (nm) (nm)(nm) (nm) Remarks 1 **X1 12 **Y1 5 present 60 130 15 — 0.310 0.090 0 0Inv. 2 **X1 12 **Y1 5 none 60 125 15 5 0.285 0.085 0 1 Inv. 3 **X1 12**Y1 5 none 60 135 25 10 0.250 0.075 1 3 Inv. 4 **X1 12 **Y1 5 none 70100 15 — 0.315 0.110 2 8 Comp. 5 **X1 12 **Y1 5 none 70 100 — — 0.3200.120 3 13 Comp. 6 **X2 10 **Y1 7 none 60 135 25 — 0.300 0.085 0 -10Inv. 7 **X2 12 **Y1 5 none 40 125 15 5 0.285 0.085 1 -1 Inv. 8 **X2 12**Y1 5 none 80 125 15 — 0.310 0.090 1 0 Inv. 9 **X2 12 **Y1 5 none 80100 15 — 0.315 0.110 2 8 Comp. 10 **X2 12 **Y1 5 none 80 100 — — 0.3200.120 3 10 Comp. 11 **X3 12 **Y2 5 none 40 135 25 10 0.250 0.075 0 -3Inv. 12 **X3 12 **Y2 5 none 40 125 15 5 0.285 0.085 1 -1 Inv. 13 **X3 12**Y2 5 none 40 125 15 — 0.310 0.090 0 0 Inv. 14 **X3 10 **Y1 6 none 40135 30 — 0.295 0.075 0 0 Inv. 15 **X3 10 **Y1 6 none 50 135 30 — 0.3000.085 0 0 Inv. 16 **X3 10 **Y1 6 none 60 135 30 — 0.300 0.085 0 0 Inv.17 **X2 6 C-7 6 none 60 135 25 — 0.305 0.075 2 7 Inv. 18 **X3 6 C-7 6none 60 125 25 — 0.300 0.085 4 8 Inv. 19 **Y1 6 C-10 6 none 60 135 25 —0.295 0.070 2 6 Inv. 20 A-4 6 **Y1 7 none 60 125 40 — 0.290 0.085 2 6Inv. 21 PL-19 8 **X1 4 none 80 130 35 — 0.305 0.090 5 3 Inv. 22 *5 5**X2 7 none 80 130 35 — 0.300 0.075 2 4 Inv. 23 *6 5 **X2 7 none 80 13035 — 0.305 0.085 3 5 Inv. 24 *6 5 **X1 5 none 80 130 35 — 0.305 0.090 53 Inv. 25 *7 5 **X2 7 none 80 130 35 — 0.305 0.085 3 5 Inv. 26 PL-8 8**X1 4 none 80 130 35 — 0.305 0.090 5 3 Inv. 27 *8 3 *9 8 none 80 160 10— 0.335 0.140 13 36 Comp. 28 *8 8 *10 3 none 80 160 10 — 0.320 0.120 535 Comp. 29 *8 8 *10 3 none 80 175 46 — 0.355 0.150 3 31 Comp. 30 **X1 7**Y1 10 none 40 130 40 5 0.285 0.090 1 -20 Inv. 31 **X1 12 **Y1 5 none40 125 35 5 0.295 0.085 0 -15 Inv. 32 **X5 12 **Y3 5 none 40 120 30 —0.305 0.095 1 -30 Inv. 33 **X4 5 **Y4 8 none 20 135 30 — 0.260 0.040 015 Inv. 34 A-31 8 **Y1 5 none 40 125 30 — 0.305 0.095 1 10 Inv. 35 A-318 **X5 7 none 40 120 30 — 0.305 0.100 2 5 Inv. 36 A-31 5 **Y2 10 none 40130 40 — 0.300 0.090 0 5 Inv. 37 A-31 5 **X1 10 none 40 130 40 — 0.3000.090 1 5 Inv. 38 A-31 10 — — none 40 130 40 — 0.310 0.100 1 20 Inv. 39A-31 10 — — none 40 100 10 — 0.320 0.150 1 20 Comp.*1: Added Amount (parts by weight),*2: Thickness of Cellulose Ester Film (μm),*3: Heat Treatment Temperature (° C.)*4: Ambient Air Replacement Frequency (times/hour)**Polymer,*5: Trimethylolpropane triacetate,*6: Trimethylolpropane acetate 2,4-dioctanoate,*7: Pentaerythritol tetraacetate*8: Triphenyl phosphate,*9: Ethylphthalyl ethyl glycolate*10: Biphenyldiphenyl phosphate,Inv.: Present Invention,Comp.: Comparative Example

Based on Table 2, it can be seen that by employing the polymersaccording to the present invention, and by controlling the free volumeradius and the half-value width, the optical anisotropy of the celluloseester film of the present invention is markedly decreased.

Example 2

<Preparation of Polarizing Plates>

By employing each of Cellulose Ester Films 1-39, 39 polarizing plateswere prepared. Subsequently, the degradation of the polarizer, thedimensional stability of the polarizing plate, and the curling of thepolarizing plate were evaluated.

A 120 μm thick polyvinyl alcohol film was immersed into 100 kg of anaqueous solution incorporating 1 kg of iodine and 4 kg of boric acid,and then stretched at a factor of 6, whereby a 25 μm thick polarizer wasprepared. One side of the resulting polarizer was allowed to adhere toeach of above Cellulose Ester Films 1-39 which had been subjected toalkali saponification, employing, as an adhesive, a 5% aqueous solutionof completely saponified type polyvinyl alcohol.

The other side of each film was allowed to adhere to an antireflectionfilm incorporating the hard coat layer described below, wherebyPolarizing Plates 1-39 were prepared. <Alkali Saponification>Saponification Process 2N—NaOH 50° C. 90 seconds Washing Process water30° C. 45 seconds Neutralization Process 10 weight % HCl 30° C. 45seconds Washing Process water 30° C. 45 seconds

Under the above conditions, a film sample was saponified, washed,neutralized, and washed in the cited order, and subsequently dried at80° C.

<Preparation of Antireflection Film>

By employing Cellulose Ester Film 1, prepared in Example 1, anantireflection film was prepared based on the following steps.

The refractive index of each layer constituting the antireflection layerwas determined based on the following method.

(Refractive Index)

The refractive index of each refractive index layer was determined basedon the measured results of the reflectance of the sample which had beenprepared in such a manner that each of the several individual layers wasapplied onto the hard coat film prepared as below, while employing aspectrophotometer. The side of each sample, opposite the side to bemeasured, was subjected to a roughening treatment, and thereafter, therear side was subjected to light absorption treatment employing a blackspray, whereby light reflection from the rear surface was minimized.Subsequently, reflectance in the visible range (400-700 nm) wasdetermined under the condition of 5-degree specular reflection,employing a spectrophotometer TYPE U-4000 (produced by Hitachi, Ltd.).

(Diameter of Minute Metal Oxide Particles)

The diameter of employed minute metal oxide particles was determined insuch a manner that each of 100 minute particles was subjected toscanning electron microscopy (SEM) and the average value of the diameterof a sphere which circumscribed each of the particles was designated asthe particle diameter.

<Preparation of Cellulose Ester Film Incorporating a Hard Coat Layer anda Back Coat Layer>

The hard coat layer liquid coating composition described below wasfiltered via a polypropylene filter at a pore diameter of 0.4 μm and wasapplied onto Cellulose Ester Film 1 prepared in Example 1, employing amicro-gravure coater. The resulting coating was dried at 90° C. andsubsequently cured under conditions in which by employing an ultravioletlamp, illuminance in the exposed area was set at 100 mW/cm² while theexposed amount was set at 0.1 J/cm², whereby a hard coat layer at adried layer thickness of 7 μm was formed and a hard coat film wasprepared.

(Hard Coat Layer Liquid Coating Composition)

The following materials were stirred and blended, whereby a hard coatlayer liquid coating composition was prepared. Acryl monomer; KAYARADDPHA 220 parts by weight (dipentaerythritol hexaacrylate, produced byNippon Kayaku Co., Ltd.) IRUGACURE 184 (produced by Ciba 20 parts byweight Specialty Chemicals Co., Ltd.) Propylene glycol monomethyl ether110 parts by weight Ethyl acetate 110 parts by weight

Further, the following back coat layer composition was applied onto theabove coating to result in a wet layer thickness of 10 μm, employing anextrusion coater. The resulting coating was dried at 85° C., and wound,whereby a back coat layer was provided. (Back Coat Layer Composition)Acetone 54 parts by weight Methyl ethyl ketone 24 parts by weightMethanol 22 parts by weight Diacetyl cellulose 0.6 part by weight 2%ultra-minute silica acetone 0.2 part by weight dispersion (AEROSIL 200V,produced by Nippon Aerosil, Co., Ltd.)<<Preparation of Antireflection Film>>

As described below, applied onto the hard coat film, prepared as above,was a high refractive index layer and subsequently was a low refractiveindex layer, whereby an antireflection layer was prepared.

<<Preparation of Antireflection Layer: High Refractive Index Layer>>

The high refractive index layer coating composition, described below,was applied onto a hard coat film employing an extrusion coater, driedat 80° C. for one minute, and subsequently cured via an exposure toultraviolet radiation at 0.1 L/cm², whereby a high refractive indexlayer was provide to result in a thickness of 78 nm.

The refractive index of the resulting high refractive index layer was1.62. <High Refractive Index Layer Coating Composition> Minute metaloxide particle isopropyl 55 parts by weight alcohol dispersion (20%solids, ITO particles at a particle diameter of 5 nm) Metal compound:Ti(OBu)4(tetra-n- 1.3 parts by weight butoxytitanium) Ionization curingtype resin: dipentaerythritol 3.2 parts by weight hexaacrylatePhotopolymerization initiator: IRUGACURE 184 (produced by 0.8 part byweight Ciba Specialty Chemicals Co., Ltd.) 10% straight chaindimethylsilicon- 1.5 parts by weight EO block polymer (FZ-2207, producedby Nippon Unicar Co., Ltd.) propylene glycol monomethyl ether liquidcomposition Propylene glycol monomethyl 120 parts by weight etherIsopropyl alcohol 240 parts by weight Methyl ethyl ketone 40 parts byweight<<Preparation of Antireflection Layer: Low Refractive Index Layer>>

The following low refractive index layer coating composition was appliedonto the above high refractive index layer, employing an extrusioncoater. After drying the resulting coating at 100° C. for one minute,curing was carried out via an exposure to ultraviolet radiation of 0.1J/cm² and thermal curing was further carried out at 120° C. for 5minutes, whereby a low refractive index layer was provided to result ina thickness of 95 nm and thus an antireflection film was prepared. Therefractive index of the above low refractive index layer was 1.37.

(Preparation of Low Refractive Index Layer Coating Composition)

<Preparation of Tetraethoxysilane Hydrolysis Product A>

A mixture prepared by blending 289 g of tetraethoxysilane with 553 g ofethanol was added to 157 g of a 0.15% aqueous acetic acid solution. Theresulting mixture was stirred for 30 hours in a 25° C. water bath,whereby Hydrolysis Product A was prepared. Tetraethoxysilane Hydrolysis110 parts by weight Product A Hollow minute silica based 30 parts byweight particle dispersion described below KBM 503 (silane couplingagent, 4 parts by weight produced by Shin-Etsu Chemical Co., Ltd.) 10%propylene glycol monomethyl 3 parts by weight ether liquid compositionof straight chain dimethylsilicone-EO block copolymer (FZ-2207, producedby Nippon Unicar Co., Ltd.) Polypropylene glycol monomethyl 400 parts byweight ether Isopropyl alcohol 400 parts by weight<Preparation of Hollow Minute Silica Based Particle Dispersion>

A mixture of 100 g of a silica sol of an average particle diameter of 5nm and a SiO₂ concentration of 20% by weight and 1900 g of pure waterwas heated to 80° C. The pH of the above reaction mother liquor was10.5. Simultaneously added to the mother liquor were 9,000 g of anaqueous 98% sodium silicate solution as SiO₂ and 9,000 g of an aqueous1.02% by weight sodium aluminate solution as Al₂O₃. During the aboveoperation, the temperature of the reaction liquor was maintained at 80°C. Immediately after the above addition, the pH of the reaction liquorincreased to 12.5 and thereafter rarely varied. After the addition, thereaction liquor was cooled to room temperature and washed employing anultrafiltration membrane, whereby an SiO₂.Al₂O₃ nucleus particledispersion at a solid concentration of 20% by weight was prepared(Process (a)).

Added to 500 g of the above nucleus particle dispersion was 1,700 g ofpure water, and the resulting mixture was heated to 98° C. Whilemaintaining the above temperature, 3,000 g of a silicic acid liquidcomposition (at an SiO₂ concentration of 3.5% by weight) which had beenprepared by de-alkalizing sodium silicate employing cation exchangeresins was added, whereby a nucleus particle dispersion, in which thefirst silica covering layer was formed, was prepared (Process (b)).

Subsequently, 1,125 g of pure water was added to 500 g of the nucleusparticle dispersion in which the silica covering layer, in which thesolid concentration reached 13% by weight, was formed by washing,employing an ultrafiltration membrane. Further, the pH was controlled to1.0 by dripping concentrated hydrochloric acid (35.5%), whereby analuminum elimination treatment was performed. Subsequently, while adding10 L of a aqueous hydrochloric acid solution at a pH of 3 and 5 L ofpure water, aluminum salts dissolved via the ultrafiltration membranewere separated, whereby a porous SiO₂.Al₂O₃ particle dispersion, inwhich some of the constituting components of nucleus particles formingthe first silica covering layer was removed, was prepared (Process (c)).

After heating, to 35° C., a mixture of 1,500 g of the above porousparticle dispersion, 500 g of pure water, 1,750 g of ethanol, and 626 gof 28% ammonia water, 104 g of ethyl silicate (28% by weight SiO₂) wasadded, whereby the second silica covering layer was formed by coveringthe surface of the porous particles which formed the first silicacovering layer with the hydrolysis polycondensation product of ethylsilicate. Subsequently, a hollow minute silica based particle dispersionat a solid concentration of 20% by weight was prepared in which thesolvent was replaced with ethanol employing an ultrafiltration membrane.

The thickness of the first silica covering layer of the above hollowminute silica based particles was 3 nm, the average particle diameterthereof was 47 nm, and MO_(x)/SiO₂ (being a mol ratio) thereof was0.0017, while the refractive index thereof was 1.28. The above averageparticle diameter was determined based on the dynamic light scatteringmethod.

<<Heating Treatment of Antireflection Film>>

The prepared antireflection film was subjected to heat treatment at 80°C. for 4 days in a heat treatment room, and was then employed to preparea polarizing plate.

<<Evaluation>>

(Rupture Problems during Preparation of Polarizing Plates)

In the above polarizing plate production process, 100 plate lots of eachof the polarizing plates were prepared and the frequency of ruptureproblems of polarizing plates was recorded and evaluated based on theevaluation criteria below.

-   A: rupture problems of polarizing plates occurred in 0-2 lots-   B: rupture problems of polarizing plates occurred in 3-5 lots-   C: rupture problems of polarizing plates occurred in 6-10 lots-   D: rupture problems of polarizing plates occurred in at least 11    lots

Subsequently, liquid crystal displays were prepared employing PolarizingPlates 1-39 prepared in Example 2.

The previously adhered polarizing plate on the viewing side was peeledfrom liquid crystal television WOOO W17-LC50 produced by Hitachi, Ltd.,which was an IPS mode type liquid crystal display, and the polarizingplate prepared as above was adhered to the glass surface of the liquidcrystal cell. During the above operation, Cellulose Ester Films 1-39prepared in Example 1 were arranged to be adhered onto the liquidcrystal cell side. In the above liquid crystal television, produced byHitachi, Ltd., employed was an immediate straight down back light.

In a bright room, a back light was continuously turned on, andvisibility at the beginning of lighting and after 100 hours was visuallyevaluated based on the following criteria.

(Visibility)

A liquid crystal display panel was visually observed and visibility wasevaluated employed the following rankings.

-   A: black looked sufficiently dense, clearness was noted, while no    color shift was noted-   B: black looked sufficiently dense, clearness was noted, while a    slight color shift was noted-   C: black did not look dense, clearness was slightly degraded, and    color shift was noted-   D: black did not look dense, clearness was degraded, and a color    shift was a major concern

Table 3 below shows the evaluation results. TABLE 3 Rupture ProblemCellulose during Liquid Ester Production of Crystal Polarizing FilmPolarizing Display Plate No. No. Plate No. Visibility Remarks 1 1 B 1 AInv. 2 2 A 2 A Inv. 3 3 A 3 A Inv. 4 4 D 4 C Comp. 5 5 D 5 D Comp. 6 6 A6 A Inv. 7 7 A 7 A Inv. 8 8 B 8 A Inv. 9 9 D 9 C Comp. 10 10 D 10 DComp. 11 11 A 11 A Inv. 12 12 A 12 A Inv. 13 13 B 13 A Inv. 14 14 A 14 AInv. 15 15 A 15 A Inv. 16 16 A 16 A Inv. 17 17 B 17 B Inv. 18 18 B 18 BInv. 19 19 B 19 B Inv. 20 20 B 20 B Inv. 21 21 B 21 B Inv. 22 22 B 22 BInv. 23 23 B 23 B Inv. 24 24 B 24 B Inv. 25 25 B 25 B Inv. 26 26 B 26 BInv. 27 27 D 27 D Comp. 28 28 D 28 D Comp. 29 29 D 29 D Comp. 30 30 A 30A Inv. 31 31 A 31 A Inv. 32 32 A 32 B Inv. 33 33 A 33 A Inv. 34 34 B 34B Inv. 35 35 B 35 B Inv. 36 36 B 36 B Inv. 37 37 B 37 B Inv. 38 38 B 38B Inv. 39 39 D 39 D Comp.Inv.: Present Invention,Comp.: Comparative Example

Polarizing plates, in which the cellulose ester film of the presentinvention was employed as a polarizing plate protective film, resultedin minimal rupture problems, and the liquid crystal displays employingthem minimized the degradation of visibility such as contrast or colorshift after turning on a back light even over an extended period oftime, whereby it was found that the above polarizing plates wereexcellent as a polarizing plate for an IPS mode type liquid crystaldisplay.

Further, it was also found that the polarizing plate protective film onthe viewing side exhibited sufficient antireflection capability.

Example 3

A Polarizing plate was prepared in the same manner as Example 2, exceptthat the polarizer employed in Polarizing Plates 1-39 was replaced withthe ethylene-modified PVA film, and evaluated in the same manner asExample 2. The polarizing plate of the present invention reproducedExample 2 and rupture problems during preparation of the polarizingplate was minimized and visibility was excellent. In addition, curlingcharacteristics of the following polarizing plates was evaluated to B-A.

<Polarizer: Preparation of Ethylene-Modified PVA Film>

Impregnated into 100 parts by weight of ethylene-modified PVA at acontent of ethylene units of 2.5 mol %, a saponification ratio of 99.95mol %, and a degree of polymerization of 2,400 were 10 parts by weightof glycerin and 170 parts by weight of water. The resulting mixture wasmelt-kneaded, degassed, melt-extruded onto a metal roller via a T die,and then cast. The thickness of the ethylene-modified PVA film, afterdrying and a heat treatment, was 40 μm and the average value of hotwater cutting temperature was 70° C.

A polarizing film was prepared in such a manner that theethylene-modified PVA film, prepared as above, was subjected to acontinuous process of preliminary swelling, dying, uniaxial stretching,fixing, drying, and a heat treatment in the cited order. In practice,the above ethylene-modified PVA film was immersed into water at 30° C.for 60 seconds to result in preliminary swelling, and subsequentlyimmersed into an aqueous solution at a boric acid concentration of 40g/liter, an iodine concentration of 0.4 g/liter, and a potassium iodideconcentration of 60 g/liter. Subsequently, the resulting film wasuniaxially stretched by a factor of 6 in a 4% boric acid aqueoussolution at 55° C., and then immersed into an aqueous solution at apotassium iodide concentration of 60 g/liter, a boric acid concentrationof 40 g/liter, and a zinc chloride concentration of 10 g/liter, all at30° C. for 5 minutes, followed by a fixing treatment. Thereafter, theresulting ethylene-modified PVA film was removed and dried at 40° C.,employing a heated air flow and further thermally treated at 100° C. for5 minutes, whereby a polarizer of a layer thickness of 15 μm wasprepared.

The transmittance and the degree of polarization of the resultantpolarizing film were 44.34% and 99.46%, respectively, while thecalculated dichroic ratio was 49.13. When the above polarizing film wasplaced at an angle of 10 degrees between two polarizing plates arrangedin the parallel to the stretching axis direction (0 degree), thedifference in luminance between the central portion and the edge portionagainst the lateral direction of the polarizing film was minimal, astargeted, and color shading was also minimal, as targeted.

<Evaluations of Curling of Polarizing Plates>

A polarizing plate cut to a 5 cm long and 1 cm wide sample was stored at25° C. and 60% relative humidity for 3 days and then moved to anambience of 25° C. and 10% relatively humidity. After 2 hours, curlingwas determined. A curl value was calculated based on the followingformula.Curl value=1/(radius of curvature (in cm) of the sample

Evaluation was performed based on the following criteria, referring tothe range of the curl value.

-   A: less than 6-   B: 6—less than 15-   C: 15—less than 60-   D: at least 60

Example 4

A liquid crystal display was prepared in the same manner as for Example3, except that liquid crystal television WOOO W17-LC50, produced byHitachi, Ltd, which was replaced with Hitachi liquid crystal televisionWOOO W32-L7000 which is an FFS mode type liquid display. Subsequently,visibility was evaluated, whereby Example 2 was reproduced and theliquid crystal display according to the present invention exhibitedexcellent visibility.

Example 5

The optical film on the viewing side of the liquid crystal cell of aliquid crystal television, FACE 23LC100, produced by Toshiba Co., Ltd.,was peeled off. In the above optical film, a polarizing plate and aretardation film were adhered. Accordingly, the above retardation filmwas peeled off and the polarizing plate was allowed to remain. Thetransparent protective film on the liquid crystal cell side of the abovepolarizing plate was peeled off and, each of Cellulose Ester Film 1prepared in Example 1 and Cellulose Ester Film 27, serving as ancomparative example was adhered as an alternate, and the peeledretardation film was adhered in the same manner as before, whereby twotypes of optical films were prepared. The resultant optical film wasadhered to the liquid crystal cell as before. Subsequently, a contrastratio in the direction inclined by 70 degrees from the normal directionat an oblique 45 degrees (in the 1 o'clock 30 minutes direction of aclock. The results showed that the contrast ration of the liquid crystalpanel, employing Cellulose Ester Film 1 of the present invention as anoptical film, was larger by a factor of 2 than the liquid crystal panelemploying Cellulose Ester Film 27 as a comparative example, whereby itwas found that the viewing angle was significantly enhanced. Thecontrast ratio was determined employing EZ CONRAST (produced by ELDICo.).

Further, the visibility was evaluated in the same manner as for Example2. The liquid crystal panel employing Cellulose Ester Film 1 of thepresent invention exhibited excellent visibility even after turning on aback light for an extended period of time.

1. A cellulose ester film exhibiting: a free volume radius of 0.25 to0.31 nm and a half-width of 0.04 to 0.1 nm, the free volume radius andthe half-width being determined by positron annihilation lifetimespectroscopy, wherein the half-width is a half-width of a graphrepresenting a relationship between relative intensity indicating aexisting probability of free volume and free volume radius; and Ro of 0to 10 nm and Rt of −30 to +20 nm, Ro and Rt being defined by thefollowing equations:Ro=(nx−ny)×d   Equation (a)Rt=((nx+ny)/2−nz)×d   Equation (b) wherein Ro represents an in-planeretardation value, Rt represents a retardation value in a thicknessdirection of the film, nx represents an in-plane refractive index in aslow axis direction, ny represents an in-plane refractive index in afast axis direction, nz represents a refractive index in the thicknessdirection of the film (each refractive index is determined at awavelength of 590 nm), and d represents a thickness of the film (nm). 2.The cellulose ester film of claim 1, wherein the film comprises, as anadditive, a polymer having a weight average molecular weight of 500 to30000, the polymer being prepared from a monomer having an ethylenicallyunsaturated bond.
 3. The cellulose ester film of claim 1 comprising anadditive selected from the group consisting of compounds represented byFormulas (1), (2), (3), (4), (5), (6), (7), (8), (9), (10), (11), (12),(13) and (14):

wherein R¹ and R² each independently represents an alkyl group which mayhave a substituent or an aryl group which may have a substituent,

wherein X² represents B, C—R (wherein R represents a hydrogen atom or asubstituent), or N; and R¹¹, R¹², R¹³, R¹⁴, R¹⁵, R²¹, R²², R²³, R²⁴,R²⁵, R³¹, R³², R³³, R³⁴, and R³⁵ each represent a hydrogen atom or asubstituent,R1—(OH)n   Formula (3) wherein R1 represents an organic group having avalence of n, and n represents an integer of 2 or more,

wherein Y³¹—Y⁷⁰ each independently represent an acyloxy group having1-20 carbon atoms, an alkoxycarbonyl group having 2-20 carbon atoms, anamido group having 1-20 carbon atoms, a carbamoyl group having 1-20carbon atoms or a hydroxyl group; V³¹—V⁴³ each independently represent ahydrogen atom or an aliphatic group having 1-20 carbon atoms; andL³¹-L⁸⁰ each independently represent a single bond or a divalentsaturated linking group having 1-40 total atoms and 0-20 carbon atoms;and V³¹—V⁴³ and L³¹-L⁸⁰ each may further have a substituent,

wherein Q¹, Q², and Q³ each independently represent a group having a 5-or 6-membered hydrocarbon ring or a 5- or 6-membered heterocycle, andthe ring may be combined with another ring to form a condensed ring, and

wherein R¹, R², and R³ each independently represents a hydrogen atom oran alkyl group having 1-5 carbon atoms; X represents a single bond, —O—,—CO—, an alkylene group, or an arylene group; and Y represents ahydrogen atom, an alkyl group, an aryl group or an aralkyl group.
 4. Thecellulose ester film of claim 1 exhibiting Rt of −20 nm≦Rt<3 nm.
 5. Apolarizing plate having the cellulose ester film of claim 1 on onesurface of a polarizing film.
 6. The polarizing plate of claim 5comprising a polarizing film containing polyvinyl alcohol, thepolarizing film having a thickness of 10 to 20 μm.
 7. The polarizingplate of claim 5 comprising a polarizing film containingethylene-modified polyvinyl alcohol.
 8. A display comprising thepolarizing plate of claim 5 and a direct backlight.